MATLAB Answers

Keep existing subplots while running code multiple times

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Hello,
I have written a code which calculates certain parameters and plots several subplots in a figure as follows:
figure('name','my_title');
h1=subplot(2,2,1);
plot (x1,y1);
h1=subplot(2,2,2);
plot(x2,y2);
h1=subplot(2,2,3);
plot(x3,y3);
h1=subplot(2,2,4);
plot(x4,y4);
Now I have to run the same code multile times for differnet data sets. I would like to keep the existing subplots (from lets say data set 1) and plot the new subplots (from lets say data set 2) on top of the existing subplots for comparison. But everytime I try to do it, its erasing the existing subplots and only plotting the current data set.
I tried to use findobj to check whether the figure exists and if so then use it as follows:
fOp.figName='my_title';
hf=findobj('Type','figure');
if ~isempty(hf)
figure(hf);hold all;
else
hf = figure('Name',fOp.figName);
hold all;
end
h1=subplot(2,2,1);
hold all;
plot (x1,y1);
h1=subplot(2,2,2);
hold all;
plot(x2,y2);
h1=subplot(2,2,3);
hold all;
plot(x3,y3);
h1=subplot(2,2,4);
hold all;
plot(x4,y4);
While it keeps the figure 1 open for the multiple runs, but it still erases the previous subplots inside the figure 1. I think I have to use 'Children' function in some way but not sure how. Any help would be much appreciated. Thank you.

  3 Comments

Mohammad Sami
Mohammad Sami on 24 Jan 2020
your reassignment h1 = subplot(2,2,1) is overwriting your previous subplot
if you keep your original assignment h1, you don't need to find the figure and then the axes.
just do hold(h1,'on')
then plot(h1,...)
and so on.
Subhasish Sutradhar
Subhasish Sutradhar on 24 Jan 2020
Thanks for the answer. I tried hold on. It didnt work. I think the problem is since I am running the code multiple times, I need a handle for the subplot just like figure.
Rik
Rik on 24 Jan 2020
@Mohammad you should post your comment as an answer. When doing so you should probably elaborate on your suggestion of using an explicit axes handle in the plot call.

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Accepted Answer

Mohammad Sami
Mohammad Sami on 25 Jan 2020
Edited: Mohammad Sami on 25 Jan 2020
You can change your code as follows.
fOp.figName='my_title';
hf = findobj('Type','figure','Name',fOp.figName);
if ~isempty(hf)
% get the handles if the figure already exist
hf = figure(hf);
h1 = hf.Children(4); % subplot 221
h2 = hf.Children(3); % subplot 222
h3 = hf.Children(2); % subplot 223
h4 = hf.Children(1); % subplot 224
else
% create figure and subplots if the figure does not exist
hf = figure('Name',fOp.figName);
h1=subplot(2,2,1);
h2=subplot(2,2,2);
h3=subplot(2,2,3);
h4=subplot(2,2,4);
end
hold(h1,'on');
plot(h1,x1,y1);
hold(h2,'on');
plot(h2,x2,y2);
hold(h3,'on');
plot(h3,x3,y3);
hold(h4,'on');
plot(h4,x4,y4);

  6 Comments

Show 3 older comments
Mohammad Sami
Mohammad Sami on 28 Jan 2020
I would suggest, convert this into a function. That way we can be more explicit about which figure you are plotting on during the for loop.
function [hf,h1,h2,h3,h4] = myplot(x1,y1,x2,y2,x3,y3,x4,y4,fOp,hf,h1,h2,h3,h4)
assert(ismember(nargin,[8 14]),'Incorrect number of arguments to this function');
if nargin <= 8 || isempty(hf)
% only x and y variables given create a new figure
hf = figure('Name',fOp.figName);
h1=subplot(2,2,1);
h2=subplot(2,2,2);
h3=subplot(2,2,3);
h4=subplot(2,2,4);
end
asse
hold(h1,'on');
plot(h1,x1,y1);
hold(h2,'on');
plot(h2,x2,y2);
hold(h3,'on');
plot(h3,x3,y3);
hold(h4,'on');
plot(h4,x4,y4);
end
You can then call this function in your for loop
num_figs; % your code here
for i = 1:num_figs;
hf = []; h1 = []; h2 = []; h3 = []; h4 = [];
fOp.figName= sprintf('my_title %i',i);
num_overlay; % your code here
for j = 1:num_overlay
% your x,y code here
[hf,h1,h2,h3,h4] = myplot(x1,y1,x2,y2,x3,y3,x4,y4,fOp,hf,h1,h2,h3,h4);
end
end
Subhasish Sutradhar
Subhasish Sutradhar on 3 Feb 2020
Thanks Mohammad. I am currently using the code with out creating a funtion. It works great. Only problem I have is to add the legend in the subplot after each run of the code. For example I would like to add legend 'data1' after the first run and then add legend 'data2' next to first legend and so on. I tried to add the legend option after the plot like:
hold(h1,'on');
plot(h1,x1,y1);
legend(h1,'legendText')% I change the legendtext manually each time before running the code
while it works for a single run, but give me following error in the next run:
Error using hold (line 83)
Unknown command option.
Error in test8 (line 891)
hold(h1,'on');
Do you know where/how I can add the legend in the code that you suggested? Thanks!
Mohammad Sami
Mohammad Sami on 4 Feb 2020
You can specify the legend in the plot command lgdtxt = 'data1'; plot(h1,x1,y1,'DisplayName',lgdtxt);
Then finally at the end just call the legend. It will use the display name property to create the legends

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