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The gchart Procedure

The gchart Procedure

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The gchart Procedure

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  1. 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: procgchartdata=save.padgett; vbar plantht; run; quit;

  2. 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.

  3. Basic Output This is kind of like a histogram, except for the spacing This value of 75 corresponds to a class ranging from 67.5 to 82.5 (with a frequency of about 60)

  4. A Few Options Sets the number of midpoints • In this version procgchartdata=save.padgett; vbar plantht/space=0type=percent levels=9; run; quit; Controls spacing between bars Changes the statistic from frequency to percent

  5. So We Get… This is a histogram

  6. Setting Midpoints • You can also set midpoints explicitly: procgchartdata=save.padgett; vbar plantht/space=0type=percent midpoints=0255075100125150; run; quit; The chart will be constructed with these 7 values as class midpoints

  7. Setting Midpoints • We might try… procformat; value classes low-<30='<30' 30-<60=’30-60' 60-<90=’60-90' 90-<120=’90-120' 120-high='>120' ; run; procgchartdata=save.padgett; vbar plantht/space=0type=percent; format plantht classes.; run; quit;

  8. We Get… SAS establishes the midpoints first then applies the format Oops

  9. The Discrete Option procgchartdata=save.padgett; vbar plantht/discretespace=0type=percent; format plantht classes.; run; quit; Discrete establishes each distinct value of the midpoint variable as a midpoint on the graph. If the variable is formatted, the formatted values are used for the construction. If you use discrete with a numeric variable you should: 1. Be sure it has only a few distinct values. or 2. Use a format to make categories for it.

  10. Result Bar width determines the space available for writing midpoint values

  11. Bar Width procgchartdata=save.plantht; vbar plantht/discretespace=0type=percent width=12; format plantht classes.; run; quit; Sets bar width

  12. Horizontal Bar Charts proc format; value $pol_type 'CO' = 'Carbon Monoxide' 'LEAD' = 'Lead' 'O3' = 'Ozone' 'SO2' = 'Sulfur Diox.'; run; procgchartdata=save.projects; hbar pol_type/discretetype=percent; format pol_type pol_type.; run; quit;

  13. Horizontal Bar Charts Besides the orientation of the bars, horizontal bar charts differ in that they produce a set of summary statistics by default. You can suppress this with the nostats option.

  14. 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.: procgchartdata=save.projects; hbar pol_type/discretesumvar=jobtotal type=meannostats; format pol_type $pol_type.; run; quit;

  15. Result Mean total cost is now summarized for each pollution type. Note: Only two types of statistics are available with summary variables, the sum (which is the default) and the mean

  16. Where to find more…

  17. 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: axisnoptions; where n is an integer between 1 and 99.

  18. Axis Modification • Lots of options can be set in an axis statement. E.g.: procgchartdata=save.projects; hbar pol_type/discretesumvar=jobtotal type=meannostats maxis=axis1 raxis=axis2; format pol_type $pol_type.; axis1label=(c=blue h=1.5f=swissb ’Type of Pollution Project'); axis2order=(0 to 100000 by 20000) minor=(n=1) value=(h=1.25f=swissb) label=(f=swissb c=red h=1.5'Mean Job Cost in Dollars'); run; quit; Assign axis statements to each chart axis Choose options/modifications for specified axis

  19. The Result

  20. 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

  21. 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

  22. Where to Find More (If you dare…)

  23. 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.

  24. Bar Fill Patterns patternid=midpoint gives each bar its own “pattern” or color

  25. Setting a Color List • The goptions statement allows us to set several global graphics options, one of which is a color list: goptionscolors=(blue red yellow cyan orange); procgchartdata=save.projects; hbar pol_type/discretesumvar=jobtotal type=meannostats maxis=axis1 raxis=axis2 patternid=midpoint; format pol_type $pol_type.; axis1label=(c=blue h=1.5f=swissb ’Type of Pollution Project'); axis2order=(0 to 100000 by 20000) minor=(n=1) value=(h=1.25f=swissb) label=(f=swissb c=red h=1.5’Mean Total Project Cost'); run; quit; This color becomes the default axis and text color

  26. 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.

  27. 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.

  28. An Example L, R and X correspond to left-leaning, right-leaning and crossed lines. The number controls the thickness 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;

  29. The group= option procgchartdata=save.padgett; hbar marsh/group=flower discretesumvar=plantht type=meannostats maxis=axis1 raxis=axis2 gaxis=axis3 patternid=midpoint; format marsh marsh. flower flower.; axis1label=(c=blue h=1.5f=swissb ’Marsh'); axis2order=(0 to 120 by 20) minor=(n=1) value=(h=1.25f=swissb) label=(f=swissb c=red h=1.5'Mean Plant Height in Centimeters'); axis3label=(c=green h=1.5f=swissb ’Flowering'); run; quit; Sets up a “grouping” variable—bars for the full set of midpoints are constructed for each value of the group variable We can modify the group axis as well

  30. Grouped Bar-Chart

  31. The subgroup= option Subgroup creates stacked bars across levels of a variable. (Not appropriate for means)

  32. 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;

  33. 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.

  34. 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.