Categorical Bar Plot keeps old categories

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I make a bar plot with categorical x-values as follows:
  • define legend names (that will be the labels for each bar in the bar graph) depending on if the value is normal or lowered (specificity to the app I am writing)
  • make the legend names categorical
  • plot them together with the heights
  • add text labels
app.legendnames = strings(app.n,1);
for i = 1:app.n
if app.loweringHeights(i)
app.legendnames(i) = strcat("P",num2str(i),"-lowered");
else %remaining plank
app.legendnames(i) = strcat('P',num2str(i));
app.bx = reordercats(categorical(app.legendnames),app.legendnames); = heights;
b = bar(app.UIAxes, app.bx,,0.5);
xtips = b(1).XEndPoints;
ytips = b(1).YEndPoints;
labels = compose("%6.0f",b(1).YData);
text(app.UIAxes, xtips,ytips,labels,'HorizontalAlignment','center','VerticalAlignment','bottom')
It looks like this
Now, when I call this plotting function again (without closing the app), each of these steps is called again. In this case, I adapt loweringHeights(2). In some way Matlab/App Designer keeps old labels that are now not anymore in use. These old labels are not part of the legendnames anymore. I know this because in other plots, the legendnames are plotted correctly. It is only in the bar graphs that I have this problem:
So I suspect the categorical thing is keeping old categories even when they are not anymore part of the new app.legendnames vector. I have no idea how to eliminate those old values. I was thinking about using removecats() but I don't see how I can tell what categories to eliminate. Any suggestions?

Answers (1)

Cris LaPierre
Cris LaPierre on 9 Nov 2021
That is the expected behavior of the categorical datatype. The list of possible categories is maintained, even if they are not present in the captured data. When creating a bar plot, the possible category names are used for X.
To get the behavior you want, use removecats to remove categories that are empty before plotting.
Cris LaPierre
Cris LaPierre on 10 Nov 2021
I see. Yes, it appears a uiaxes is combining the categories from the previous bar plot and the current one. I can't say if that is intentional or not, but it is different behavior than what happens in a figure axes. I believe your workaround is the best solution currently (R2021b).

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