The gchart Procedure
The gchart Procedure is used to create bar charts of various types (it can also create pie charts.
It’s most basic form would look something like this:
proc gchart data=save.padgett;vbar plantht;
run;quit;
The gchart Procedure
The vbar (or hbar) statement includes a variable that is referred to as the midpoint variable.
If this variable is of the character type, a midpoint is established for each unique value.
If it is numeric, SAS establishes classes or bins for it.
In either case, the frequency in each class is summarized by vertical (or horizontal) bars.
Basic Output
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This is kind of likea histogram, except
for the spacingThis value of 75
corresponds to aclass ranging from
67.5 to 82.5(with a frequency
of about 60)
A Few Options
In this version
proc gchart data=save.padgett;
vbar plantht/space=0 type=percent levels=9;
run;
quit;Controls spacing between bars
Changes the statistic from frequencyto percent
Sets the number of midpoints
So We Get…
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This is a histogram
Setting Midpoints
You can also set midpoints explicitly:
proc gchart data=save.padgett;
vbar plantht/space=0 type=percent
midpoints=0 25 50 75 100 125 150;
run;
quit; The chart will be constructedwith these 7 values as class
midpoints
Setting Midpoints We might try…
proc format;value classes
low-<30='<30'30-<60=’30-60'60-<90=’60-90'90-<120=’90-120'120-high='>120';
run;
proc gchart data=save.padgett;vbar plantht/space=0 type=percent;format plantht classes.;
run;quit;
We Get…
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Oops
SAS establishesthe midpoints first
then applies the format
The Discrete Option
proc gchart data=save.padgett;
vbar plantht/discrete space=0 type=percent;
format plantht classes.;
run;
quit; Discrete establishes each distinctvalue of the midpoint variable asa midpoint on the graph. If the
variable is formatted, the formattedvalues are used for the construction.
If you use discrete witha numeric variable you
should:1. Be sure it has only a
few distinct values.or
2. Use a format to makecategories for it.
Result
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Bar width determinesthe space available forwriting midpoint values
Bar Width
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proc gchart data=save.plantht;vbar plantht/discrete space=0 type=percent
width=12;format plantht classes.;
run;quit;
Sets bar width
Horizontal Bar Charts
proc format;value $pol_type 'CO' = 'Carbon Monoxide' 'LEAD' =
'Lead' 'O3' = 'Ozone' 'SO2' = 'Sulfur Diox.';run;
proc gchart data=save.projects;
hbar pol_type/discrete type=percent;
format pol_type pol_type.;
run;
quit;
Horizontal Bar Charts
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Besides the orientationof the bars, horizontal barcharts differ in that they
produce a set of summarystatistics by default.
You can suppress this withthe nostats option.
Summary Variables If I want my bar chart to summarize values
of some analysis variable for each midpoint, use the sumvar= (and type= ) option.
E.g.:
proc gchart data=save.projects;
hbar pol_type/discrete sumvar=jobtotal type=mean nostats;
format pol_type $pol_type.;
run;
quit;
Result
Note: Only two types of statisticsare available with summary variables,
the sum (which is the default) andthe mean
Mean total cost isnow summarized foreach pollution type.
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Axis Modification
The two axes on the bar graph are referred to as the midpoint axis (maxis) and the response axis (raxis).
Axes can be modified with axis statements. The general form of an axis statement is:
axisn options;
where n is an integer between 1 and 99.
Axis Modification
Lots of options can be set in an axis statement. E.g.:
proc gchart data=save.projects;hbar pol_type/discrete sumvar=jobtotal type=mean
nostats maxis=axis1 raxis=axis2;format pol_type $pol_type.;axis1 label=(c=blue h=1.5 f=swissb ’Type of Pollution Project');axis2 order=(0 to 100000 by 20000) minor=(n=1) value=(h=1.25 f=swissb)
label=(f=swissb c=red h=1.5 'Mean Job Cost in Dollars');
run;quit;
Assign axis statementsto each chart axis
Choose options/modificationsfor specified axis
Some Options
c= sets axis color
w=sets axis width
label=(options) Sets axis label, some options:
h= text height c= text color f= font style ‘Any Text’ is the axis label (overrides any label
currently assigned) a= angle of the label text r= rotation of individual characters
Some Options
value =(options) controls appearance of axis values, options are
similar to those for label. order=(a to b by c)
sets axis starting and ending points and increment minor=(options) major=(options)
Controls style of major or minor tick marks. Some options: n= number of ticks (for minor it’s the number between
major ticks) h= height c= color w= width
Bar Fill Patterns
In all charts to this point, all bars have been red. It is possible to change the color, and it is possible to give each bar a different color.
To give bars different colors, specify patternid=midpoint in the hbar or vbar statement.
Bar Fill Patterns
patternid=midpointgives each bar its own
“pattern” or color
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Setting a Color List
The goptions statement allows us to set several global graphics options, one of which is a color list:
goptions colors=(blue red yellow cyan orange);proc gchart data=save.projects;
hbar pol_type/discrete sumvar=jobtotal type=mean nostatsmaxis=axis1 raxis=axis2
patternid=midpoint;format pol_type $pol_type.;axis1 label=(c=blue h=1.5 f=swissb ’Type of Pollution Project');axis2 order=(0 to 100000 by 20000)
minor=(n=1) value=(h=1.25 f=swissb) label=(f=swissb c=red h=1.5 ’Mean Total Project Cost');
run;quit;
This color becomesthe default axis and
text color
Setting a Color List
Remember, setting a color is an option for any axis statement, so if you change the color list, you can always override the first color behavior in the axis statement.
coutline= is an option you can use in the vbar or hbar statement to set the bar outline color.
Alternate Fill Patterns
You can specify some alternate fill patterns for bars (particularly useful for creating black & white charts) with a pattern statement(s).
The two major options in the pattern statement are c= and v=, for color and fill, respectively. Rules: If no color is specified, the fill pattern is applied
for each color in the color list. If a color is specified, the fill pattern is applied
only once. The fill pattern can be set to on of Ln, Rn or Xn;
where n is an integer between 1 and 5.
An Example
L, R and Xcorrespond
to left-leaning,right-leaningand crossedlines. The
numbercontrols the
thickness
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Add these pattern statements to your previous code to get the above bar graph:
pattern c=black v=L1; pattern c=black v=R1;
pattern c=black v=X1; pattern c=black v=L5;
pattern c=black v=R5;
The group= option
proc gchart data=save.padgett;hbar marsh/group=flower discrete sumvar=plantht type=mean
nostats maxis=axis1 raxis=axis2 gaxis=axis3 patternid=midpoint;
format marsh marsh. flower flower.;axis1 label=(c=blue h=1.5 f=swissb ’Marsh');axis2 order=(0 to 120 by 20) minor=(n=1) value=(h=1.25 f=swissb)
label=(f=swissb c=red h=1.5 'Mean Plant Height in Centimeters');axis3 label=(c=green h=1.5 f=swissb ’Flowering');
run;quit; Sets up a “grouping” variable—bars for the
full set of midpoints are constructed for eachvalue of the group variable
We can modify thegroup axis as well
The subgroup= option
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Subgroup creates stacked bars across levels
of a variable. (Not appropriate for means)
The subgroup= option
proc gchart data=save.padgett; hbar marsh/group=flower discrete type=percent nostats maxis=axis1 raxis= axis2 gaxis=axis3 patternid=subgroup subgroup=form legend=legend1; format marsh $marsh. flower $flower.; axis1 label=(c=blue h=1.5 f=swissb 'Marsh'); axis2 order=(0 to 50 by 10) minor=(n=1) value=(h=1.25 f=swissb) label=(f=swissb c=red h=1.5 ); axis3 label=(c=green h=1.5 f=swissb 'Flowering');legend1 across=1 label=(c=blue 'Form of Plant') frame cshadow=gray position=(top right) mode=share;
Legend Modifications
In a legend statement, some options available are: label= similar to what is available in the axis
statement. across= and down= sets limit for row or
column length in the legend (only use one) frame draws a border around the legend cshadow= places a shadow “behind” the
legend in the specified color.
Legend Modifications
position=( ) places the legend, choices include: inside/outside left/right/center top/bottom/middle (default is bottom center outside).
mode= tells how to allocate space for the chart and legend, choices are: reserve: sets aside space for the legend before graph
is drawn (can’t be used with position set to inside) share or protect: allows graph and legend to use the
same space. Share has the graph drawn over the legend if they intersect, protect does the opposite.