MATLAB Answers

Why am I getting two different plots for the exact same matrix?

2 views (last 30 days)
John Vargas
John Vargas on 8 Aug 2018
Commented: Walter Roberson on 10 Aug 2018
Hello, I am trying to plot these two matrices. One of them (BFF) I made myself while the other one (SF) is one i found, but I have compared the two and they should be the same (which is what I want, to replicate the Matrix SF). I made the matrix BFF from the vector fM1S1, but when I try to plot the two exact matrix, I get completely different results. Why?

  5 Comments

Show 2 older comments
John Vargas
John Vargas on 8 Aug 2018
I am sorry, I am not sure how to upload the full file since it exceeds the 5 MB, but I will upload them separately. I basically used the 'reshape' command to make the matrix BFF.
John Vargas
John Vargas on 8 Aug 2018
Here is the single vector I am using to make BFF. Also, @OCDER, I used the 'isequal' command and got a value of 0, meaning they are not equal but they should be. Earlier I used the ' == ' command to check if the matrix were equal and they seemed to match.
Walter Roberson
Walter Roberson on 9 Aug 2018
>> max(BFF(:)-SF(:))
ans =
0.00204231
Perhaps you are encountering noticeable round-off error. If you entered data from a printed table, the table might not have shown all of the decimal places the data really had, and that can result in calculations not coming out as you expect them to.

Sign in to comment.

Answers (1)

Thorsten
Thorsten on 8 Aug 2018
Maybe it helps if you transpose the matrix to get it right.

  4 Comments

Show 1 older comment
Thorsten
Thorsten on 8 Aug 2018
If they are not equal, how large is the difference? Maybe it is just a few eps.
John Vargas
John Vargas on 9 Aug 2018
I plotted the two matrices to show how far off the results were and as you can see from the picture, I believe the different is very large.
Walter Roberson
Walter Roberson on 10 Aug 2018
As outsiders, we have no reason to expect that the two matrices should be the same.
>> max(BFF(:))
ans =
0.00204256
>> max(SF(:))
ans =
2.5e-07
>> min(BFF(:))
ans =
0
>> min(SF(:))
ans =
0
You can see from these values that it is pretty certain that there will be some point where the difference between the two exceeds 0.002, or roughly a factor of 8000 compared to the smaller matrix.

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by