Adding Percent Sign to Labels in Bar Graph

[Erika Kociolek]

I'd like to display the labels for the bar graph below as percents (with a "%" sign after them), but don't know how to do this beyond manually adding them using blabel().

I am looking for a solution that's automated. Please correct me if this is wrong, but I don't think that there is a way to format variables to include percents that would then show up in a graph (as there is for commas).

sysuse auto, clear
generate p_over_5k = 0
replace p_over_5k = 1 if price > 5000
generate mileage = "Low" if mpg < 20
replace mileage = "High" if mpg >= 20
generate ones = 1
collapse (sum) ones p_over_5k, by(foreign mileage)
generate pr_over_5k = round(p_over_5k/ones, 0.01)*100
graph bar (asis) pr_over_5k, over(foreign) over(mileage) asyvars blabel(bar) ytitle("Percent of Cars Over $5,000")

Thank you for any assistance you can provide,
Erika

[Sergiy Radyakin]

Dear Erika, something like this? Thanks for providing a starter. Sergiy.

sysuse auto, clear
generate p_over_5k = 0
replace p_over_5k = 1 if price > 5000
generate mileage = "Low" if mpg < 20
replace mileage = "High" if mpg >= 20
generate ones = 1
collapse (sum) ones p_over_5k, by(foreign mileage)
generate pr_over_5k = round(p_over_5k/ones, 0.01)*100
graph bar (asis) pr_over_5k, over(foreign) over(mileage) asyvars blabel(bar) ytitle("Percent of Cars Over $5,000")

local nb=`.Graph.plotregion1.barlabels.arrnels'
forval i=1/`nb' {
  di "`.Graph.plotregion1.barlabels[`i'].text[1]'"
  .Graph.plotregion1.barlabels[`i'].text[1]="`.Graph.plotregion1.barlabels[`i'].text[1]'%"
}
.Graph.drawgraph

[Erika Kociolek]

Thank you for this information and solution, Sergiy. Can you explain a bit more about how this loop works? It looks like it's calling specific elements of the graph, but I'm not familiar with the term "arrnels" (in the first line of the new code) or this method for modifying a graph.

And can you confirm that there isn't a way to format a variable to include a percent sign (as there is with commas)?

Thank you again,
Erika

[Nick Cox]

Adding percent signs doesn't count as a Stata format. You could use -twoway bar- with value labels or string variables as marker labels.

[Sergiy Radyakin]

Thank you for this information and solution, Sergiy. Can you explain a bit more about how this loop works? It looks like it's calling specific elements of the graph, but I'm not familiar with the term "arrnels" (in the first line of the new code) or this method for modifying a graph.

And can you confirm that there isn't a way to format a variable to include a percent sign (as there is with commas)?

Thank you again,
Erika

Erika,

1) the loop works with the graph labels directly attaching the percent sign to every original label. Code like this requires knowledge of the internals of Stata graphics. This is advanced stuff and it is not documented. It just works.
For arrnels on the other hand: see the class programming manual. In this case it is just a number of labels.
You may do any transformations to the original labels (multiply/divide by 100, check for empty labels, attach $, % or something else, etc depending on the task).

2) Yes, just as Nick has already confirmed, you can't create a format containing % in Stata.

Best, Sergiy

[boriskaiser]

Dear Sergiy,

How do I have to adjust your loop for it to work in a combined graph with two bar charts?

Many thanks,
Boris

[Sergiy Radyakin]

Boris, notice how Erika has started her question with a starter code. Doing this increases the chances of response greatly. Best, Sergiy Radyakin

clear all
sysuse auto, clear
generate p_over_5k = 0
replace p_over_5k = 1 if price > 5000
generate mileage = "Low" if mpg < 20
replace mileage = "High" if mpg >= 20
generate ones = 1
collapse (sum) ones p_over_5k, by(foreign mileage)
generate pr_over_5k = round(p_over_5k/ones, 0.01)*100
graph bar (asis) pr_over_5k, over(foreign) over(mileage) asyvars blabel(bar) ytitle("Percent of Cars Over $5,000") name(G1)
graph bar (asis) pr_over_5k, over(foreign) over(mileage) asyvars blabel(bar) ytitle("Percent of Cars Over $5,000") name(G2) bar(1,color(green)) bar(2,color(yellow)) 

graph combine G1 G2

local ng=`.Graph.graphs.arrnels'
forval g=1/`ng' {
    local nb=`.Graph.graphs[`g'].plotregion1.barlabels.arrnels'
    forval i=1/`nb' {
      di "`.Graph.graphs[`g'].plotregion1.barlabels[`i'].text[1]'"
      .Graph.graphs[`g'].plotregion1.barlabels[`i'].text[1]="`.Graph.graphs[`g'].plotregion1.barlabels[`i'].text[1]'%"
    }
}
.Graph.drawgraph

[Nick Cox]

If you use twoway bar instead, you can knit your own bar label. This uses Sergiy's example, except that it doesn't show two versions of the same graph. No need for graph editor adjustments.

clear all
set scheme s1color 
sysuse auto, clear

generate mileage = mpg >= 20 
label def mileage 0 "Low" 1  "High"
label val mileage mileage 

egen pc_over_5k = mean(100 * (price > 5000)), by(foreign mileage) 
gen tolabel = string(pc_over_5k, "%2.0f") + "%" 

twoway bar pc_over_5k mileage, base(0) barw(0.5) bfcolor(green*0.2)  ///
by(foreign, note("") legend(off)) ///
|| scatter pc_over_5k mileage, ms(none) ysc(r(0 105)) yla(0(20)100) ///
mlabel(tolabel) mlabpos(12) mlabcolor(black) xla(0 1, tlcolor(none) valuelabel) ///
ytitle(% of cars > USD 5000)

[Kenzie Reid]

How could we use a similar code to the one Sergiy Radyakin shared to add percent symbols to the height labels of a histogram? Here is an example where I have height labels, but I would like to be able to add the percent symbol without doing it manually for each. Unfortunately, the code for the bar graph doesn't work with a histogram, and while I generally don't love histograms, there are times when they are useful.

sysuse auto, clear
hist mpg, percent addlabels addlabopts(mlabformat(%4.1fc))

[Hemanshu Kumar]

sysuse auto, clear
twoway__histogram_gen mpg, frac gen(h x)
replace h = h*100
gen h_str = strofreal(h,"%3.1f") + "%" 
twoway bar h x, mlabel(h_str) barwidth(`=x[2]-x[1]') xlabel(10(10)40) ytitle("Percent") scheme(s1color) color(gs6) mlabcolor(black)

which produces

[Nick Cox]

#9 and #10 To spell it out, you don't need Graph Editor trickery because histogram belongs to the twoway family so adding marker labels directly is possible. In fact #10 is neater than #8 in how that was done.

[Kenzie Reid]

Interesting thank you. I understand that you're manually creating the label here, but when I copy the exact syntax into my Stata window there are no labels that appear on the bar. Why not?

sysuse auto, clear

twoway__histogram_gen mpg, frac gen(h x)
    replace h = h*100
    gen h_str = strofreal(h,"%3.1f") + "%"

twoway bar h x, ///
        mlabel(h_str) mlabcolor(black) ///
        barwidth(`=x[2]-x[1]') ///
        xlabel(10(10)40) ytitle("Percent") ///
        scheme(s1color) color(gs6)

Produced the attached graphic. What am I missing here?