Using hold and plotyy in a loop

I am having trouble getting matlab to update plotyy in a loop.

I want extend a line of data as my code advance in time.

This is easily done for a single plot, as shown below for a simplified extract of my code

for year=1:1:year_max
  %***Do Calcs
  CalcStuff(year)

    %***plot
    figure(1)

    subplot(3,1,[2 3]);  cla;  hold on;
     %some stuff

    subplot(311); hold on; 
    plot(year/1000,sum(State.Ice),'k.');
     xlabel('Time (kyrs BP)')
     ylabel ('Total Ice Mass')
    drawnow;
 end;

However, the similar code below for two lines using plotyy() is broken. The first Data point appears and STAYS on the plot (great), but all subsequent data are overwritten each loop (BAD!!).

for year=1:1:year_max
  %***Do Calcs
  CalcStuff(year)

    %***plot
    figure(1)

    subplot(3,1,[2 3]);  cla;  hold on;
     %some stuff

    subplot(311); hold on; 
     [ax,h1,h2]=plotyy(year/1000,sum(State.Ice),year/1000,CO2ppmv);
     set(h1, 'linestyle', '.','color','k'); set(ax(1), 'ycolor', 'k')
     set(h2, 'linestyle', '.','color','r'); set(ax(2), 'ycolor', 'r')
     hold(ax(1));hold(ax(2));
     xlabel('Time (kyrs BP)')
     ylabel ('Total Ice Mass')
    drawnow;
 end;

Any thoughts on how to fix this would be gratefully received!!

Answer 1

[Walter Roberson]

hold(ax(1), 'on'); hold(ax(2), 'on');

When you do not specify 'on' or 'off' the default is to toggle between on and off

[Jonathan]

Thanks for the suggestion.

It partially fixes the problem. ax(1) will now show all data, but ax(2) does not; despite them both receiving the same hold on command