Help finding error in Matlab code

I have two sets of code, one in Python and the other in Matlab. I am converting Python to Matlab, but ran into a error that I am having a difficult time trouble shooting. There erros is...

Index exceeds matrix dimensions.

Error in unSteadyTEvortexShedding (line 167)

                    [xVV(i, j), yVV(i, j)] = VortexPointOnPt(xVorPos(i),

                    yVorPos(i), xVorPos(j), yVorPos(j), 0);

I have attached the VortexPointOnPt function file as well. The indexing is occurring at the while loop with k or the for loops?

[OCDER]

To help with debugging, you need to format the code in unSteadTEvortexShedding. It's hard to determine which loop is starting where because the end statements aren't aligned. I see a recycling of for loop variables, which could cause the error.

Where is the end of this if/else statement?

 for i = 1:t
            for j = 1:t
                if i == j
                    xVV(i, j) = yVV(i,j)  == 0;
                else
                    ...

   wakePanelStr = 0.1;
   xpWake1 = xp(end);

Try not to override counter variables. Example, this for loop seems to be within another for loop with the same i counter variable

 for i = 1:t
    for j = 1:t
        ...
    for i = 1:numPanels  %THIS "i" replaced the other "i"
            [tWP(i), nWP(i)] = VortexPointOnPt(xc(i), yc(i), xcWake, ycWake, theta(i));

What are these "end" ending in your function?

        end
            end
        end
       end

    end

                end
            end
        end
     end
        end
    end
end

[Jan]

This will not the source of errors, but

filepath = savepath('C:/FramesMatlab')

saves the folders of the current Matlab path to a pathdef.m file in the folder 'C:/FramesMatlab'. This is meaningless.

[Zach Dunagan]

Both of you make some great points. Jan, what is the Matlab equivalent to that of Python?

Donald, I got the code to run. Thank you for your suggestions. I was just not thinking clearly.

[Jan]

@Zach: The equivalent of what in Python? All I see is a meaningless Matlab command:

filepath = savepath('C:/FramesMatlab')

But I cannot know, which Python command you want to replace. Perhaps:

pathName='C://Users//Zach Dunagan//Desktop//frames//'

Then:

filepath = 'C:/FramesMatlab';

Answer 1

[Jan]

You define xVorPos and yVorPos:

xVorPos = zeros(numFrames, 1);
yVorPos = zeros(numFrames, 1);

Then you run a loop:

for t = 1:numFrames % for each time frame

Inside this loop you check

    if t > 0

repeatedly, but this is impossible, when the loop runs from 1:numFrames. Omit this tests to reduce clutter. You access:

for j =1:t
  ... xVorPos(j), yVorPos(j)

before the failing line successfully. Therefor I cannot imagine, why

for i = 1:t
          for j = 1:t
              if i == j
                  xVV(i, j) = yVV(i,j)  == 0;
              else
                  [xVV(i, j), yVV(i, j)] = VortexPointOnPt(xVorPos(i), yVorPos(i), ...
                                                           xVorPos(j), yVorPos(j), 0);

fails some lines later.

What is the purpose of:

xVV(i, j) = yVV(i,j)  == 0;

This sets xVV(i,j) to 1, if yVV(i,j) is 0, and to 1 otherwise. Is this wanted? If so, it is strange, because you have defined

        xVV = zeros(t, t);
        yVV = zeros(t, t);

explicitly. Or do you want to set xVV(i,j) and yVV(i,j) both to zeros? If so, omit this, because the zeros set this value already.

There are so many strange and confusing commands in your code, that I think the most efficient way to debug it is to delete it and rewrite in in Matlab from scratch. Digging in the mud does not produce reliable and clean code. You cannot write an English article by typing it in German, use Google's auto-translator and fix the errors afterwards.

[Zach Dunagan]

I told Donald I found the bug in the previous comment.

The code I am referring to is... pathName='C://Users//Zach Dunagan//Desktop//frames//'

You said perhaps it would be... filepath = 'C:/FramesMatlab'

Thank you.

Answer 2

[Walter Roberson]

As I described in a previous question, in Python, setting pathName is just setting a variable, with no side effects and no special meaning. It is just another variable name. It is also unused in the code you posted, so you can simply delete the line.

[Zach Dunagan]

Walter this is what I am trying to do.

From whom I am working under. "It's a string that is the path for where to save the images. So you should have a similar string variable in your matlab code that is used when you save the images."

Can someone help me with the last set of if else statements between the Python and Matlab code?

This is what I recently changed it to...

% calculate wake panel strength

         if k == 1

              if t == 1

                  wakePanelStr = -x(end) * perimeter

              else

                  wakePanelStr = -x(end) * perimeter - sum(vortStrength(1:t));

              end

         else

              abs(currCircSum) > 10^(-14)

              wakePanelStr = wakePanelStr - currCircSum / ((currCircSum - prevCircSum) / (wakeStrSto(k, t) - wakeStrSto(k - 1, t)));

         end

I am getting an error at the end saying Error using reshape To RESHAPE the number of elements must not change. I attached a new script file because I added more code to the end.

[Walter Roberson]

"It's a string that is the path for where to save the images. "

But nothing in that code saves images.

[Walter Roberson]

         else

              abs(currCircSum) > 10^(-14)

should be

         elseif abs(currCircSum) > 10^(-14)

[Zach Dunagan]

What about the reshape error?

[Walter Roberson]

You are not passing nPanels in to PanelCoorToNTCoor() so it is not obvious to me that the second output of that routine (which I do not see the code for) will have nPanels rows.

[Zach Dunagan]

I manage to figure it out.

[Zach Dunagan]

I found the bug.