How about using: https://www.mathworks.com/matlabcentral/fileexchange/26161-roman2num-and-num2roman-modern-roman-numerals
I'm not sure what problem you had with the other submission because you didn't provide much detail about why it was no use. But I'd image the code would:
- make the plot
- get the values of ticks on the y axis
- make sure that the 'mode' is manual (so that the ticks don't change). It's always wise to set the tick values explicitly or set the mode when setting tick labels, otherwise if the ticks change things will likely look weird
- convert the values
- set the ticklabels
plot(...)
tickvals = yticks;
yticks manual
romanvals = num2roman(tickvals);
yticklabels(romanvals);
