`g_cdf(G;S;O;X)`

Returns the cumulative frequency distribution of values within a given group.

Function type

Vector only

Syntax

g_cdf(G;S;O;X)
t_cdf(X)

Input

Argument	Type	Description
`G`	any	A space- or comma-separated list of column names Rows are in the same group if their values for all of the columns listed in `G` are the same. If `G` is omitted, all rows are considered to be in the same group. If any of the columns listed in `G` contain N/A, the N/A value is considered a valid grouping value.
`S`	integer	The name of a column in which every row evaluates to a 1 or 0, which determines whether or not that row is selected to be included in the calculation If `S` is omitted, all rows will be considered by the function (subject to any prior row selections). If any of the values in `S` are neither 1 nor 0, an error is returned.
`O`	integer or decimal	A space- or comma-separated list of column names that determine the row order within a particular group Note: The `O` parameter has no effect and may be omitted.
`X`	any numeric type	A column name

Return Value

For every row in each group defined by G (and for those rows where S=1, if specified), g_cdf returns a decimal value corresponding to the fraction of valid (non-N/A) values of X within the group that are less than or equal to the current value of X.

Note: g_cdf(G;S;O;X) is equivalent to g_cumfreq(G;S;O;X)/g_valcnt(G;S;X).

Sample Usage

<base table="pub.doc.samples.ref.func.g_func_time_series_sample_usage"/>
<willbe name="g_cdf_1" value="g_cdf(state;include;order;value)"/>
<willbe name="g_cdf_2" value="g_cdf(state city;include;order;value)"/>

Example

Let's use the Hourly U.S. Weather (1990) table (pub.demo.weather.hourly90) to demonstrate the use of g_cdf(G;S;O;X).

Let's say we want to find out, for every hour of a particular day, the percentage of hours of the day that it rained as much or less.

For demonstration purposes, let's select one particular day at one particular station, and we'll display only those columns that are relevant to this example.

<base table="pub.demo.weather.hourly90"/>
<sel value="(date=19900224)"/>
<sel value="(id=25339)"/>
<colord cols="id,date,hour,prec"/>

This will give us the following:

Note: prec is the hourly precipitation measured in .01 inches.

Let's create a computed column for the results of g_cdf(G;S;O;X). Since we've already selected the rows that we want for our group, we can omit the G parameter. We'll also omit the S parameter, since we want to consider all rows in this group. We can also omit the O parameter since it has no effect for this function. Finally, we'll specify the prec column for X since we want to calculate the cumulative frequency distribution of precipitation.

<willbe name="cumfreq_amt" value="g_cdf(;;;prec)" format="type:pct;dec:2"/>

Note: We specify format="type:pct;dec:2" so that the results will be displayed as a percentage with two decimal places of precision.

This will give us the following:

This new column shows, for example, that at 10 a.m. on 2/24/90, it rained .12 inches, and that 45.83% of the hours in that day it rained that much or less.

Additional Information

The t_ version of this function defaults the G argument and omits the S and O arguments. The default for G is set at table load time based on the organization of the table.