[dygraphs.git] / docs / data.html

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    <title>dygraphs input types</title>
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    <h2>dygraphs Data Format</h2>

    <p>When you create a Dygraph object, your code looks something like
    this:</p>

    <code>
      g = new Dygraph(document.getElementById("div"),
                      <i>data</i>,
                      { <i>options</i> });
    </code>

    <p>This document is about what you can put in the <i>data</i>
    parameter.</p>

    <p>There are five types of input that dygraphs will accept:</p>
    <ol>
      <li><a href="#csv">CSV data</a>
      <li><a href="#url">URL</a>
      <li><a href="#array">array (native format)</a>
      <li><a href="#function">function</a>
      <li><a href="#datatable">DataTable</a>
    </ol>

    <p>These are all discussed below. If you're trying to debug why your input
    won't parse, <b>check the JS error console</b>. dygraphs tries to log
    informative errors explaining what's wrong with your data, and these can
    often point you in the right direction.</p>

    <p>There are several options which affect how your input data is
    interpreted. These are:
    <ul>
      <li> <i>xValueParser</i> affects CSV only.
      <li> <i>errorBars</i> affects all input types.
      <li> <i>customBars</i> affects all input types.
      <li> <i>fractions</i> affects all input types.
      <li> <i>labels</i> affects all input types.
    </ul>
    </p>

    <a name="csv"><h3>CSV</h3>
    <p>Here's an example of what CSV data should look like:</p>
    <pre>
    Date,Series1,Series2
    2009/07/12,100,200  # comments are OK on data lines
    2009/07/19,150,201
    </pre>

    <p>"CSV" is actually a bit of a misnomer: the data can be tab-delimited,
    too. The delimiter is set by the <i>delimiter</i> option. It default to ",".
    If no delimiter is found in the first row, it switches over to tab.</p>

    <p>CSV parsing can be split into three parts: headers, x-value and
    y-values.</p>

    <h4>Headers</h4>
    <p>If you don't specify the <i>labels</i> option, dygraphs will look at the
    first line of your CSV data to get the labels. If you see numbers for series
    labels when you hover over the dygraph, it's likely because your first line
    contains data but is being parsed as a label. The solution is to either add
    a header line or specify the labels like this:</p>

    <code>
      new Dygraph(el,
                  "2009/07/12,100,200\n" +
                  "2009/07/19,150,201\n",
                  { labels: [ "Date", "Series1", "Series2" ] });
    </code>

    <h4>x-values</h4>
    <p>Once the headers are parsed, dygraphs needs to determine what the type of
    the x values is. They're either dates or numbers. To make this
    determination, it looks at the first column of the first row ("2009/07/12"
    in the example above). Here's the heuristic: if it contains a '-' or a '/',
    or otherwise doesn't parse as a float, the it's a date. Otherwise, it's a
    number.</p>

    <p>Once the type is determined, that doesn't mean all the values will parse
    correctly. The general rule is:<p>

    <ul>
      <li>For dates, your strings have to be parseable by <i>Date.parse</i>.
      <li>For numbers, your strings have to be parseable by <i>parseFloat</i>.
    </ul>

    <p>You can manually verify this using a JavaScript console. If a value
    doesn't parse, dygraphs will put a warning about it on your console. But
    beware: different browsers support different date formats!</p>

    <p>Here are some valid date formats:</p>
    <ul>
      <li>2009-07-12</li>
      <li>2009/07/12</li>
      <li>2009/07/12 12</li>
      <li>2009/07/12 12:34</li>
      <li>2009/07/12 12:34:56</li>
    </ul>

    <p>If you specify the <i>xValueParser</i> option, then all this detection is
    bypassed and your function is called instead. Your parser function takes in
    a string and needs to return a number. For dates/times, you should return
    milliseconds since epoch. You may also want to specify a few other options
    to make sure that everything gets displayed properly.<p>

    <p>Here's code which parses a CSV file with unix timestamps in the first
    column:</p>

    <code>
      new Dygraph(el,
                  "Date,Series1,Series2\n" +
                  "1247382000,100,200\n" +
                  "1247986800,150,201\n",
                  {
                    xValueFormatter: Dygraph.dateString_,
                    xValueParser: function(x) { return 1000*parseInt(x); },
                    xTicker: Dygraph.dateTicker
                  });
    </code>

    <h4>y-values</h4>
    <p>Dependent (y-axis) values are simpler than x-values because they're
    always numbers. The complexity here comes from the various ways that you can
    specify the uncertainty in your measurements.<p>

    <p>If your y-values are just numbers, then they need to be parseable by
    JavaScript's parseFloat function. Acceptable formats include:</p>

    <ul>
      <li>12
      <li>-12
      <li>12.
      <li>12.3
      <li>1.24e+1
      <li>-1.24e+1
    </ul>

    <p>If you have missing data, just leave the column blank (your CSV file will
    probably contain a ",," in it).</p>

    <p>If your numbers have uncertainty associated with them, then there are
    three basic ways to express this: using fractions, standard deviations or
    explicit ranges.</p>

    <h5>Fractions</h5>
    <p>If you specify the <i>fractions</i> option, then your data will all be
    interpreted as ratios between zero and one. This is often the case if you're
    plotting a percentage.</p>

    <code>
      new Dygraph(el,
                  "X,Frac1,Frac2\n" +
                  "1,1/2,3/4\n"+
                  "2,1/3,2/3\n"+
                  "3,2/3,17/49\n"+
                  "4,25/30,100/200",
                  { fractions: true });
    </code>

    <p>Why not just divide the fractions out yourself? There are two attractive
    reasons not to:</p>

    <ul>
      <li>If you set both <i>fractions</i> and <i>errorBars</i>, then the
    denominator is interpreted as a sample size and dygraphs will plot <a
      href="http://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval">Wilson
      binomial proportion confidence intervals</a> around each point.

      <li>If you set <i>showRoller</i>, then dygraphs will combine the values as
      fractions. If two point are <i>a/b</i> and <i>c/d</i>, it will plot
      <i>(a+b) / (c+d)</i> rather than <i>(a/b + c/d) / 2</i>, which is what
      you'd get if you divided the fractions through. This will also shrink the
      confidence intervals.</li>
    </ul>

    <h5>Standard Deviations</h5>
    <p>Often you have a measurement and also a measure of its uncertainty: a
    standard deviation. If you specify the <i>errorBars</i> option, dygraphs
    will look for alternating value and standard deviation columns in your CSV
    data.  Here's what it should look like:</p>

    <code>
      new Dygraph(el,
                  "X,Y1,Y2\n" +
                  "1,10,5,20,5\n" +
                  "2,12,5,22,5\n",
                  { errorBars: true });
    </code>

    <p>The "5" values are standard deviations. When each point is plotted, a
    2-standard deviation region around it is shaded, resulting in a 95%
    confidence interval. If you want more or less confidence, you can set the
    <i>sigma</i> option to something other than 2.0.</p>

    <p>When you roll data with standard deviations, dygraphs will plot the
    average of your values in each rolling period and the RMS value of your
    standard deviations: sqrt(std1 + std2 + std3 + ... + stdN)/N.</p>

    <h5>Custom error bars</h5>
    <p>Sometimes your data has asymetric uncertainty or you want to specify
    something else with the error bars around a point. One example of this is
    the "temperatures" demo on the <a href="http://danvk.org/dygraphs">dygraphs
      home page.</a>, where the point is the daily average and the bars denote
    the low and high temperatures for the day.</p>

    <p>To specify this format, set the <i>customBars</i> option. Your CSV values
    should each be three numbers separated by semicolons ("low;mid;high").
    Here's an example:</p>

    <code>
      new Dygraph(el,
                  "X,Y1,Y2\n" +
                  "1,10;20;30,20;5;25\n" +
                  "2,10;25;35,20;10;25\n",
                  { customBars: true });
    </code>

    <p>The middle value need not lie between the low and high values. If you set
    a rolling period, the three values will all be averaged independently.</p>


    <a name="url"><h3>URL</h3>
    <p>If you pass in a URL, dygraphs will issue an XMLHttpRequest for it and
    attempt to parse the returned data as CSV.
    </p>

    <p><i>Common problems</i>. Make sure the URL is accessible and returns data
    in text format (as opposed to a CSV file with an HTML header). You can see
    what the response looks like by checking your JS console or by requesting
    the URL yourself.</p>


    <a name="array"><h3>Array (native format)</h3>
    <p>If you'll be constructing your data set from a server-side program (or
    from JavaScript) then you're better off producing an array than CSV data.
    This saves the cost of parsing the CSV data and also avoids common parser
    errors.</p>

    <p>The downside is that it's harder to look at your data (you'll need to use
    a JS debugger) and that the data format is a bit less clear for values with
    uncertainties.</p>

    <p>Here's an example of "native format":</p>

    <code>
      new Dygraph(document.getElementById("graphdiv2"),
                  [
                    [1,10,100],
                    [2,20,80],
                    [3,50,60],
                    [4,70,80]
                  ],
                  {
                    labels: [ "x", "A", "B" ]
                  });
    </code>

    <h4>Headers</h4>
    <p>Headers for native format must be specified via the <i>labels</i>
    option. There's no other way to set them.</p>

    <h4>x-values</h4>
    <p>If you want your x-values to be dates, you'll need to use specify a Date
    object in the first column. Otherwise, specify a number. Here's a sample
    array with dates on the x-axis:</p>

    <code>
      [
        [ new Date("2009/07/12"), 100, 200 ],
        [ new Date("2009/07/19"), 150, 220 ]
      ]
    </code>

    <h4>y-values</h4>
    <p>You can specify <i>errorBars</i>, <i>fractions</i> or <i>customBars</i>
    with the array format. If you specify any of these, the values become arrays
    (rather than numbers). Here's what the format looks like for each one:</p>

    <code>
      <i>errorBars</i>: [x, [value1, std1], [value2, std2], ...]
      <i>fractions</i>: [x, [num1, den1], [num2, den2], ...]
      <i>customBars</i>: [x, [low1, val1, high1], [low2, val2, high2], ...]
    </code>

    <p>To specify missing data, set the value to null. You may not set a value
    inside an array to null. Use null instead of the entire array.</p>

    <a name="function"><h3>Functions</h3>

    <p>You can specify a function that returns any of the other types. If
    <i>x</i> is a valid piece of dygraphs input, then so is</p>

    <code>
      function() { return x; }
    </code>

    <a name="datatable"><h3>DataTable</h3>
    <p>You can also specify a Google Visualization Library <a
      href="http://code.google.com/apis/visualization/documentation/reference.html#DataTable">DataTable</a>
    object as your input data. This lets you easily switch between dygraphs and
    other gviz visualizations such as the Annotated Timeline. It also lets you
    embed a Dygraph in a Google Spreadsheet.</p>

    <p>You'll need to set your first column's type to one of "number", "date"
    or "datetime".</p>

    <pre>
    DataTable TODO:
    - When to use Dygraph.GvizWrapper
    - how to specify fractions
    - how to specify missing data
    - how to specify value + std. dev.
    - how to specify [low, middle, high]
    - walkthrough of embedding a gadget in google docs/on a web page
    - walkthrough of using std. dev. in a spreadsheet chart
    </pre>

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Commit	Line	Data
53e5cec3	1	<!DOCTYPE html>
708cbe06 DV	2	<html>
708cbe06 DV	3	<head>
10494b48	4	<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7; IE=EmulateIE9">
708cbe06 DV	5	<title>dygraphs input types</title>
708cbe06 DV	6	<style type="text/css">
f10f06f5 DV	7	code { white-space: pre; border: 1px dashed black; display: block; }
	8	pre { white-space: pre; border: 1px dashed black; }
	9	body { max-width: 800px; }
708cbe06 DV	10	</style>
	11	</head>
	12	<body>
	13	<h2>dygraphs Data Format</h2>
	14
	15	<p>When you create a Dygraph object, your code looks something like
	16	this:</p>
	17
	18	<code>
	19	g = new Dygraph(document.getElementById("div"),
	20	<i>data</i>,
	21	{ <i>options</i> });
	22	</code>
	23
	24	<p>This document is about what you can put in the <i>data</i>
	25	parameter.</p>
	26
	27	<p>There are five types of input that dygraphs will accept:</p>
	28	<ol>
f10f06f5 DV	29	<li><a href="#csv">CSV data</a>
	30	<li><a href="#url">URL</a>
	31	<li><a href="#array">array (native format)</a>
	32	<li><a href="#function">function</a>
	33	<li><a href="#datatable">DataTable</a>
708cbe06 DV	34	</ol>
	35
	36	<p>These are all discussed below. If you're trying to debug why your input
	37	won't parse, <b>check the JS error console</b>. dygraphs tries to log
	38	informative errors explaining what's wrong with your data, and these can
	39	often point you in the right direction.</p>
	40
	41	<p>There are several options which affect how your input data is
	42	interpreted. These are:
	43	<ul>
	44	<li> <i>xValueParser</i> affects CSV only.
	45	<li> <i>errorBars</i> affects all input types.
	46	<li> <i>customBars</i> affects all input types.
	47	<li> <i>fractions</i> affects all input types.
	48	<li> <i>labels</i> affects all input types.
	49	</ul>
	50	</p>
	51
f10f06f5	52	<a name="csv"><h3>CSV</h3>
708cbe06 DV	53	<p>Here's an example of what CSV data should look like:</p>
	54	<pre>
	55	Date,Series1,Series2
	56	2009/07/12,100,200 # comments are OK on data lines
	57	2009/07/19,150,201
	58	</pre>
	59
	60	<p>"CSV" is actually a bit of a misnomer: the data can be tab-delimited,
	61	too. The delimiter is set by the <i>delimiter</i> option. It default to ",".
	62	If no delimiter is found in the first row, it switches over to tab.</p>
	63
	64	<p>CSV parsing can be split into three parts: headers, x-value and
	65	y-values.</p>
	66
	67	<h4>Headers</h4>
	68	<p>If you don't specify the <i>labels</i> option, dygraphs will look at the
	69	first line of your CSV data to get the labels. If you see numbers for series
	70	labels when you hover over the dygraph, it's likely because your first line
	71	contains data but is being parsed as a label. The solution is to either add
	72	a header line or specify the labels like this:</p>
	73
	74	<code>
	75	new Dygraph(el,
	76	"2009/07/12,100,200\n" +
	77	"2009/07/19,150,201\n",
	78	{ labels: [ "Date", "Series1", "Series2" ] });
	79	</code>
	80
	81	<h4>x-values</h4>
	82	<p>Once the headers are parsed, dygraphs needs to determine what the type of
	83	the x values is. They're either dates or numbers. To make this
	84	determination, it looks at the first column of the first row ("2009/07/12"
	85	in the example above). Here's the heuristic: if it contains a '-' or a '/',
	86	or otherwise doesn't parse as a float, the it's a date. Otherwise, it's a
	87	number.</p>
	88
	89	<p>Once the type is determined, that doesn't mean all the values will parse
	90	correctly. The general rule is:<p>
	91
	92	<ul>
	93	<li>For dates, your strings have to be parseable by <i>Date.parse</i>.
	94	<li>For numbers, your strings have to be parseable by <i>parseFloat</i>.
	95	</ul>
	96
	97	<p>You can manually verify this using a JavaScript console. If a value
	98	doesn't parse, dygraphs will put a warning about it on your console. But
	99	beware: different browsers support different date formats!</p>
	100
	101	<p>Here are some valid date formats:</p>
	102	<ul>
	103	<li>2009-07-12</li>
	104	<li>2009/07/12</li>
	105	<li>2009/07/12 12</li>
	106	<li>2009/07/12 12:34</li>
	107	<li>2009/07/12 12:34:56</li>
	108	</ul>
	109
	110	<p>If you specify the <i>xValueParser</i> option, then all this detection is
	111	bypassed and your function is called instead. Your parser function takes in
	112	a string and needs to return a number. For dates/times, you should return
	113	milliseconds since epoch. You may also want to specify a few other options
	114	to make sure that everything gets displayed properly.<p>
	115
	116	<p>Here's code which parses a CSV file with unix timestamps in the first
117	column:</p>
118
119	<code>
120	new Dygraph(el,
121	"Date,Series1,Series2\n" +
122	"1247382000,100,200\n" +
123	"1247986800,150,201\n",
124	{
125	xValueFormatter: Dygraph.dateString_,
126	xValueParser: function(x) { return 1000*parseInt(x); },
127	xTicker: Dygraph.dateTicker
128	});
129	</code>
130
131	<h4>y-values</h4>
132	<p>Dependent (y-axis) values are simpler than x-values because they're
133	always numbers. The complexity here comes from the various ways that you can
134	specify the uncertainty in your measurements.<p>
135
136	<p>If your y-values are just numbers, then they need to be parseable by
137	JavaScript's parseFloat function. Acceptable formats include:</p>
138
139	<ul>
140	<li>12
141	<li>-12
142	<li>12.
143	<li>12.3
144	<li>1.24e+1
145	<li>-1.24e+1
146	</ul>
147
148	<p>If you have missing data, just leave the column blank (your CSV file will
149	probably contain a ",," in it).</p>
150
151	<p>If your numbers have uncertainty associated with them, then there are
152	three basic ways to express this: using fractions, standard deviations or
153	explicit ranges.</p>
154
155	<h5>Fractions</h5>
156	<p>If you specify the <i>fractions</i> option, then your data will all be
157	interpreted as ratios between zero and one. This is often the case if you're
158	plotting a percentage.</p>
159
160	<code>
161	new Dygraph(el,
162	"X,Frac1,Frac2\n" +
163	"1,1/2,3/4\n"+
164	"2,1/3,2/3\n"+
165	"3,2/3,17/49\n"+
166	"4,25/30,100/200",
167	{ fractions: true });
168	</code>
169
170	<p>Why not just divide the fractions out yourself? There are two attractive
171	reasons not to:</p>
172
173	<ul>
174	<li>If you set both <i>fractions</i> and <i>errorBars</i>, then the
175	denominator is interpreted as a sample size and dygraphs will plot <a
176	href="http://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval">Wilson
177	binomial proportion confidence intervals</a> around each point.
178
179	<li>If you set <i>showRoller</i>, then dygraphs will combine the values as
180	fractions. If two point are <i>a/b</i> and <i>c/d</i>, it will plot
181	<i>(a+b) / (c+d)</i> rather than <i>(a/b + c/d) / 2</i>, which is what
182	you'd get if you divided the fractions through. This will also shrink the
183	confidence intervals.</li>
184	</ul>
185
186	<h5>Standard Deviations</h5>
187	<p>Often you have a measurement and also a measure of its uncertainty: a
188	standard deviation. If you specify the <i>errorBars</i> option, dygraphs
189	will look for alternating value and standard deviation columns in your CSV
190	data. Here's what it should look like:</p>
191
192	<code>
193	new Dygraph(el,
194	"X,Y1,Y2\n" +
195	"1,10,5,20,5\n" +
196	"2,12,5,22,5\n",
197	{ errorBars: true });
198	</code>
199
200	<p>The "5" values are standard deviations. When each point is plotted, a
201	2-standard deviation region around it is shaded, resulting in a 95%
202	confidence interval. If you want more or less confidence, you can set the
203	<i>sigma</i> option to something other than 2.0.</p>
204
205	<p>When you roll data with standard deviations, dygraphs will plot the
206	average of your values in each rolling period and the RMS value of your
207	standard deviations: sqrt(std1 + std2 + std3 + ... + stdN)/N.</p>
208
209	<h5>Custom error bars</h5>
210	<p>Sometimes your data has asymetric uncertainty or you want to specify
211	something else with the error bars around a point. One example of this is
212	the "temperatures" demo on the <a href="http://danvk.org/dygraphs">dygraphs
213	home page.</a>, where the point is the daily average and the bars denote
214	the low and high temperatures for the day.</p>
215
216	<p>To specify this format, set the <i>customBars</i> option. Your CSV values
217	should each be three numbers separated by semicolons ("low;mid;high").
218	Here's an example:</p>
219
220	<code>
221	new Dygraph(el,
222	"X,Y1,Y2\n" +
223	"1,10;20;30,20;5;25\n" +
224	"2,10;25;35,20;10;25\n",
225	{ customBars: true });
226	</code>
227
228	<p>The middle value need not lie between the low and high values. If you set
229	a rolling period, the three values will all be averaged independently.</p>
230
231
f10f06f5	232	<a name="url"><h3>URL</h3>
708cbe06 DV	233	<p>If you pass in a URL, dygraphs will issue an XMLHttpRequest for it and
	234	attempt to parse the returned data as CSV.
	235	</p>
	236
	237	<p><i>Common problems</i>. Make sure the URL is accessible and returns data
	238	in text format (as opposed to a CSV file with an HTML header). You can see
	239	what the response looks like by checking your JS console or by requesting
	240	the URL yourself.</p>
	241
	242
f10f06f5	243	<a name="array"><h3>Array (native format)</h3>
708cbe06 DV	244	<p>If you'll be constructing your data set from a server-side program (or
	245	from JavaScript) then you're better off producing an array than CSV data.
	246	This saves the cost of parsing the CSV data and also avoids common parser
	247	errors.</p>
	248
	249	<p>The downside is that it's harder to look at your data (you'll need to use
	250	a JS debugger) and that the data format is a bit less clear for values with
	251	uncertainties.</p>
	252
f10f06f5	253	<p>Here's an example of "native format":</p>
708cbe06	254
f10f06f5 DV	255	<code>
	256	new Dygraph(document.getElementById("graphdiv2"),
	257	[
	258	[1,10,100],
	259	[2,20,80],
	260	[3,50,60],
	261	[4,70,80]
	262	],
	263	{
	264	labels: [ "x", "A", "B" ]
	265	});
	266	</code>
708cbe06	267
f10f06f5 DV	268	<h4>Headers</h4>
	269	<p>Headers for native format must be specified via the <i>labels</i>
	270	option. There's no other way to set them.</p>
	271
	272	<h4>x-values</h4>
	273	<p>If you want your x-values to be dates, you'll need to use specify a Date
	274	object in the first column. Otherwise, specify a number. Here's a sample
	275	array with dates on the x-axis:</p>
708cbe06	276
f10f06f5 DV	277	<code>
	278	[
	279	[ new Date("2009/07/12"), 100, 200 ],
	280	[ new Date("2009/07/19"), 150, 220 ]
	281	]
	282	</code>
	283
	284	<h4>y-values</h4>
	285	<p>You can specify <i>errorBars</i>, <i>fractions</i> or <i>customBars</i>
	286	with the array format. If you specify any of these, the values become arrays
	287	(rather than numbers). Here's what the format looks like for each one:</p>
	288
	289	<code>
	290	<i>errorBars</i>: [x, [value1, std1], [value2, std2], ...]
	291	<i>fractions</i>: [x, [num1, den1], [num2, den2], ...]
	292	<i>customBars</i>: [x, [low1, val1, high1], [low2, val2, high2], ...]
	293	</code>
	294
	295	<p>To specify missing data, set the value to null. You may not set a value
	296	inside an array to null. Use null instead of the entire array.</p>
	297
	298	<a name="function"><h3>Functions</h3>
	299
	300	<p>You can specify a function that returns any of the other types. If
	301	<i>x</i> is a valid piece of dygraphs input, then so is</p>
	302
	303	<code>
	304	function() { return x; }
	305	</code>
	306
	307	<a name="datatable"><h3>DataTable</h3>
	308	<p>You can also specify a Google Visualization Library <a
	309	href="http://code.google.com/apis/visualization/documentation/reference.html#DataTable">DataTable</a>
	310	object as your input data. This lets you easily switch between dygraphs and
	311	other gviz visualizations such as the Annotated Timeline. It also lets you
	312	embed a Dygraph in a Google Spreadsheet.</p>
	313
	314	<p>You'll need to set your first column's type to one of "number", "date"
	315	or "datetime".</p>
	316
	317	<pre>
	318	DataTable TODO:
708cbe06 DV	319	- When to use Dygraph.GvizWrapper
	320	- how to specify fractions
	321	- how to specify missing data
	322	- how to specify value + std. dev.
	323	- how to specify [low, middle, high]
	324	- walkthrough of embedding a gadget in google docs/on a web page
	325	- walkthrough of using std. dev. in a spreadsheet chart
f10f06f5	326	</pre>
708cbe06	327
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