How to only plot the better result from a loop of 48 iterations in a convergence plot?

hi, I'm running a complex program and i am required to plot the output of the program(resistance) in a convergence plot. if the first result is 900, if should only plot the lower resistance. Meaning, if the second iteration gives a result of 1000, the plot should remaina straight line at 900 under it reaches a value of less than 900. I have 48 results that i need to sort in a plot in this manner. Any ideas? Thank you

Answer 1

[Jon]

You could do something like this, assuming that your output is in vector y and iteration number is in vector iterCount

plot(iterCount,min(y,900))

[Sasthikapreeya D/O Ponnarasu]

hi, my output is in a single column in 48x4 cell and I've tried this using this command. The plot generated shows only the plots for the results less than 900 but the plot line only remains at 900 and does not remain at the next lower value generated. Do you know how i can get the line to remain at the lower value until the next lower value is reached? Thank you!

plot(min(cell2mat(fitness(2:end,2)),900));

[Jon]

So do I understand correctly that you only want to plot a point if it is less than or equal all of the points before it?

If so you could do something like this

% get the column of interest
y = fitness(2:end,2); 

% make some values for the x-axis in the plot
iteration = 1:length(y)

% preallocate logical array that indicates if a point should be included in plot
iplt = true(size(y));

% loop through the points and only include them in plot if they show an improvement
for k = 2:length(y)
    iplt(k) = y(k)<=min(y(1:k-1)); 
end
plot(iteration,y,iteration(iplt),y(iplt))

There might be some clever way to vectorize this and avoid the loop, but I think this should do what you want.

[Sasthikapreeya D/O Ponnarasu]

Hi, I did not manage to do it this way, had errors about logic. However, I managed to use a different approach by creating conditions then plotting it. Thank you for your help!

[Jon]

I'm glad you got it working, but I'm curious about what "errors about logic" you had. I had run my suggested code on a little test program and it seemed to work as intended. Maybe there are some differences in the details of how you are handling the data.