How to draw vertical lines in between categorical x-axis ticks

I have some data that I display using the plot function, with categorical labels on the x-axis. I would like to draw vertical lines in between some of the x-axis tick marks, but not all. I would appreciate suggestions on how to do this. I'm using Matlab 2017a.

I can easily draw a vertical line exactly on the x-axis tick marks, using something like this:

   plot([xNames(5), xNames(5)],[0 1],'k')

where xNames is my array with the categorical names. But I would like to adjust this so that a vertical line is drawn between, e.g., xNames(5) and xNames(6).

Answer 1

[HW]

I figured it out; the key is to not plot with categorical axis too early. I did something like

plot(1:34, 2*[1:34],'ko')
set(gca,'XTick',1:34)
hold on, plot([3.5 3.5],[-0.5 0.5],'k')
hold on, plot([6.5 6.5],[-0.5 0.5],'k')
hold on, plot([20.5 20.5],[-0.5 0.5],'k')
hold on, plot([30.5 30.5],[-0.5 0.5],'k')
set(gca,'XTickLabel',string(xNames))
xtickangle(45)

[Jos (10584)]

the repeated hold on and plot(..) commands can be replaced by using

gridxy([3.5 6.5 20.5 30.5]), 'color', 'k')

(see link in my answer)

Answer 2

[Jos (10584)]

Use the average?

v = (xNames(5)+ xNames(6))/2
plot([v v], ...)

You might also be interested in various utilities on the File Exchange that can plot vertical and horizontal grid lines at specific places, like my own GRIDXY

https://uk.mathworks.com/matlabcentral/fileexchange/9973-gridxy

[HW]

That doesn't seem like it will work, as xNames is a categorical array.

[Jos (10584)]

insert a new category name between 5 and 6 and use that?

[HW]

I really would like to have the line to be drawn between two tick marks. I would prefer to not add anything visual to the x-axis, even additional tick marks.