Double y-axis plot

Hi I have a 495x4 matrix. In column 1 are datenum values, column 2,3 and 4 contain data. I want to plot the data from all 3 columns on one plot. The data from column 2 and 3 should be for the y-axis on the left and the data from column 4 for the y-axis on the right. I should therefore have 3 lines on the plot.

I know it is possible to plot 2 lines with plotyy. How would I plot 3 lines ? Is it possible to do this a different way ?

I am using MATLAB 2011b

[Adam]

R2016a and later has yyaxis which would allow you to do this I think, but in R2011b you would probably have to program it yourself by creating two axes in the same location as each other I would guess.

[David du Preez]

Thanks. I thought that might be the case. The difficult part is to add the third line.

[Adam]

You can add two lines on a single axes easily enough using

doc hold

whether or not you have another line on a different axes that happens to be in the same location.

Doing it yourself the more difficult part is just dealing with getting the axis ticks on the right side and not having both grids on at the same time etc.

[dpb]

Use plotyy, the pre-HG2 yyaxis

Answer 1

[dpb]

"column 1 are datenum values, ... column 2 and 3 ... on the left and ... column 4 on the right"

Nothing to it... :)

[hAx,hL1,hL2]=plotyy(data(:,1),data(:,2:3),data(:,1),data(:,4));
set(hAx(2),'xtick','[])           % just don't show but one x axis ticks, etc., ...
linkaxes(hAx,'x')                 % and link the two so stay in synch on limits, etc., ...
datetick(hAx,'x','keeplimits')    % and turn to date format

May need to change format and number ticks, etc., to match the data but that's the starting point