How to use legend command

Hello all

I am having the data lets say for seven elements and I am ploting it using a loop in a single figure. But in these seven elements someof the elements contain nothing and then the plot for that is not plotted. Now how I can use the legend command only for the elements that are plotted?

Please guide!!!

Regards

Answer 1

[Mahdi]

Is the loop still telling the figure to plot even if there isn't any data recorded? You have a few ways around it:

The first one basically tells the legend to put an "empty" headline for the second item (if nothing was plotted)

legend('item1', '', 'item3')

You can also only tell MATLAB to plot only when there is data with

if isempty(your_matrix)~=1
plot(x,y)
end

There are also other ways which you can tell the legend to ignore some entries. You can also enter the plot tools (in the top menu of figure) and do it without code.

[Sameer]

Hello thanks for replying.I am adding a code to givethe clear picture.

for p=0:count_ports-1

     if (SRE(:,p+1)&SPDP(:,p+1)&SYfit(:,p+1))==0

         continue

     else    

        plot(SRE(:,p+1),SPDP(:,p+1),'*',SRE(:,p+1),SYfit(:,p+1));

        hold on

end

end

%x-Axis:

xlabel('Reynolds Number');

%y-Axis:

ylabel('Pressure (Pa)');

filename= sprintf('Plot_of_element%d',el);

hold off

saveas(gcf,filename,'jpg');

where SRE,SPDP,SYfit are the matrices.

I hope withthis youcanguide me better.

Regards

[Mahdi]

Wouldn't just adding

legend('item1', 'item2', 'item3')

in your case after the loop solve the problem? If I'm understanding it correctly, I would also change the if statement to be | (or) statements instead of and statements:

if SRE(:,p+1)==0|SPDP(:,p+1)==0|SYfit(:,p+1))==0

[Sameer]

Hi...thanks,it should be OR...can you tell me how i can form the loop for legend as ´there will be a lot of data and thus I want a generalization such as sprintf('Element%',p). but I amnot able to generate a loop that work with legend. Please Guide I am a newbie to matlab.

Regards

[Mahdi]

Do you mean that you want the legend to be labelled differently based on the loop?

You can simply do something like this: (this is just an example)

for i=1:3
figure(i)
var1=sprintf('Plot_%d', i)
% Do your plotting here 
legend(var1)
end

In this case, the legend would show Plot_1, Plot_2, Plot_3