How to Subplot in a for loop

I need help with making a subplot for the two histograms this code creates

%% Setting Initial Conditions
clc %Clearing the command window.
clear all %Making output nicer.
%0 is a step to the left and 1 is a step to the right. 
Left = 0; %Setting the initial left value.
Right = 0; %Setting the initial right value. 

%% Creating the Ensemble of Random Walkers
for N = [25000, 100000] %Creating a vector for all the ensemble sizes.
for x = 1:N %Creating an ensemble of N walkers.
for i = 2:2501 %Setting the for loop to run 2500 times. 
    Walker = -1 + rand(1)*(2); %Setting the walker to be a random number between -1 or 1.
    if Walker > 0 %Saying if the walker takes a step to the right.
        Left(i) = Left(i-1); %Left number of steps stays the same.
        Right(i) = Right(i-1) + Walker; %Right number of steps goes up by walker value.
    elseif Walker < 0 %Saying if the walker takes a step to the left.
        Left(i) = Left(i-1) + Walker; %Left number of steps goes up by walker value.
        Right(i) = Right(i-1); %Right number of steps stay the same.
    end %Ending the if statement.
end %Ending the for loop.
location = Right(end) - abs(Left(end)); %Making the location the right number of steps minus the left.
Finallocation(x) = location; %Setting the location to be the end values of the walkers.
end %Ending the for loop.
%% Plotting the Results
figure('Name','Ensemble Histogram') %Labeling the figure appropriately.
histogram(Finallocation,20) %Making a histogram of the final locations.
z1 = sprintf('Ensemble of step size = %d',N); %Making a title that updates as variables are changed.
title(z1) %Making z1 the title.
xlabel('Final Location') %Labeling the x-axis appropriately.
ylabel('Number of Walkers') %Labeling the y-axis appropriately. 
end %Ending the for loop.

[Image Analyst]

You have 3 nested for loops. What do you want to plot, and where?

[Patrick Keaveney]

I want to do a subplot for the two histograms of "Finallcation". I would prefer to plot them outside the for loops if possible.

Answer 1

[Sriram Tadavarty]

Hi Patrick,

You can the following modifications to the code:

1) To plot it inline the for loops, you can use the count temporary variable, bring the figure command before the for loop, as code below (%%% annotated for the comments placed) :

%% Setting Initial Conditions
clc %Clearing the command window.
clear all %Making output nicer.
%0 is a step to the left and 1 is a step to the right. 
Left = 0; %Setting the initial left value.
Right = 0; %Setting the initial right value. 

count = 1; %%% Initialized count
figure('Name','Ensemble Histogram') %Labeling the figure appropriately. %%% Brought it before for loop
%% Creating the Ensemble of Random Walkers
for N = [25000, 100000] %Creating a vector for all the ensemble sizes.
for x = 1:N %Creating an ensemble of N walkers.
for i = 2:2501 %Setting the for loop to run 2500 times. 
    Walker = -1 + rand(1)*(2); %Setting the walker to be a random number between -1 or 1.
    if Walker > 0 %Saying if the walker takes a step to the right.
        Left(i) = Left(i-1); %Left number of steps stays the same.
        Right(i) = Right(i-1) + Walker; %Right number of steps goes up by walker value.
    elseif Walker < 0 %Saying if the walker takes a step to the left.
        Left(i) = Left(i-1) + Walker; %Left number of steps goes up by walker value.
        Right(i) = Right(i-1); %Right number of steps stay the same.
    end %Ending the if statement.
end %Ending the for loop.
location = Right(end) - abs(Left(end)); %Making the location the right number of steps minus the left.
Finallocation(x) = location; %Setting the location to be the end values of the walkers.
end %Ending the for loop.;
%% Plotting the Results
subplot(2,1,count) %%% Subplot calling
histogram(Finallocation,20) %Making a histogram of the final locations.
z1 = sprintf('Ensemble of step size = %d',N); %Making a title that updates as variables are changed.
title(z1) %Making z1 the title.
xlabel('Final Location') %Labeling the x-axis appropriately.
ylabel('Number of Walkers') %Labeling the y-axis appropriately. 
count = count+1; %%% count variable update
end %Ending the for loop.

2) To plot outside the for loops, here you need to split up and write the code twice as placed below:

%% Setting Initial Conditions
clc %Clearing the command window.
clear all %Making output nicer.
%0 is a step to the left and 1 is a step to the right. 
Left = 0; %Setting the initial left value.
Right = 0; %Setting the initial right value. 

count = 1;
NVal  =[25000, 100000];
%% Creating the Ensemble of Random Walkers
for N = [25000, 100000] %Creating a vector for all the ensemble sizes.
for x = 1:N %Creating an ensemble of N walkers.
for i = 2:2501 %Setting the for loop to run 2500 times. 
    Walker = -1 + rand(1)*(2); %Setting the walker to be a random number between -1 or 1.
    if Walker > 0 %Saying if the walker takes a step to the right.
        Left(i) = Left(i-1); %Left number of steps stays the same.
        Right(i) = Right(i-1) + Walker; %Right number of steps goes up by walker value.
    elseif Walker < 0 %Saying if the walker takes a step to the left.
        Left(i) = Left(i-1) + Walker; %Left number of steps goes up by walker value.
        Right(i) = Right(i-1); %Right number of steps stay the same.
    end %Ending the if statement.
end %Ending the for loop.
location = Right(end) - abs(Left(end)); %Making the location the right number of steps minus the left.
Finallocation{count}(x) = location; %Setting the location to be the end values of the walkers.
end %Ending the for loop.;
%% Plotting the Results 
count = count+1;

end %Ending the for loop.

figure('Name','Ensemble Histogram') %Labeling the figure appropriately.
subplot(2,1,1)
histogram(Finallocation{1},20) %Making a histogram of the final locations.
z1 = sprintf('Ensemble of step size = %d',NVal(1)); %Making a title that updates as variables are changed.
title(z1) %Making z1 the title.
xlabel('Final Location') %Labeling the x-axis appropriately.
ylabel('Number of Walkers') %Labeling the y-axis appropriately.
subplot(2,1,2)
histogram(Finallocation{2},20) %Making a histogram of the final locations.
z1 = sprintf('Ensemble of step size = %d',NVal(2)); %Making a title that updates as variables are changed.
title(z1) %Making z1 the title.
xlabel('Final Location') %Labeling the x-axis appropriately.
ylabel('Number of Walkers') %Labeling the y-axis appropriately.

If the values of N are more to use, i suggest the first method itself, to make the plot inline the for. Just update the values in subplot accordingly.

Hope this helps.

Regards,

Sriram

[Patrick Keaveney]

Thank you. This does help.