Matlab Coding Display Help

2021 11 2
2 个回答
更新时间：2021 11 3
5 次查看（30 天）

0 个投票

I have this code:
function [A] = Gauss_Elim(A)
%Performs Gaussian Elimination%
N = length(A);
tol = 1e-6;
%for each pivot along the diagonal
for ii = 1:N-1
%for each row under the pivot
for jj=ii+1:N
if abs(A(jj,ii)) > tol
%factor is ratio between pivot value
%and entry below pivot in row jj
fac=A(ii,ii)/A(jj,ii);
%row replacement
A(jj,:) = fac*A(jj,:)-A(ii,:);
end
end
end
end
This code produces the correct answer, but how would I display the steps the code takes to get the correct answer?

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回答（2 个）

Dave B
Dave B 2021-11-2
Ran in:

1 个投票

Ran in:
Do you mean you would like to see what's in A on each iteration? Here's 4-5 ways depending on how complicated you want it to be (I'll just do the full code and run it for the last one!)
  • You can remove the ; at the end of the line
A(jj,:) = fac*A(jj,:)-A(ii,:)
  • You can add the line disp(A)
A(jj,:) = fac*A(jj,:)-A(ii,:);
disp(A)
  • You could show it graphically by adding a call to imagesc on each iteration of the loop
A(jj,:) = fac*A(jj,:)-A(ii,:);
imagesc(A) % consider specifying CLim on the axes, as this will be changing on each iteration...
  • For the image solution, you might consider storing the (step-wise) output of A so that you can play the movie again later, or write it to a video file, etc.
function [B,A] = Gauss_Elim(A)
...
B=nan(N,N,sum(1:N)+1);
cnt=1;
for ii = 1:N-1
...
A(jj,:) = fac*A(jj,:)-A(ii,:);
B(:,:,cnt)=A;
cnt=cnt+1;
...
  • You could plot each step into a separate subplot (this could get slow if you have a large matrix)
Gauss_Elim(rand(10))
ans = 10×10
0.3995 0.4408 0.4586 0.4269 0.1814 0.0349 0.4339 0.6469 0.4362 0.6070 0 -0.3572 -0.1512 -0.1629 -0.1583 0.0285 -0.4141 -0.3145 -0.0164 -0.5157 0 0 -0.1919 0.1574 -0.0239 0.5764 0.3408 0.4011 0.2645 -0.1513 0 0 0 0.7394 0.1896 0.2065 1.1101 0.4552 -1.9977 1.2333 -0.0000 0 0 0 -0.9684 1.1577 -0.3696 1.7478 3.2485 -1.8617 0.0000 0 0 0 0.0000 -5.2155 -0.2409 -1.6482 -7.9881 3.7745 -0.0000 0 0 0 -0.0000 0 0.1991 0.1445 0.2797 0.4623 -0.0000 0 0 0 -0.0000 0 -0.0000 -1.9966 -2.5243 -5.4185 -0.0000 0 -0.0000 0.0000 -0.0000 0 0.0000 0.0000 17.8712 1.0736 0.0000 0 0.0000 -0.0000 0.0000 0 0.0000 -0.0000 0 28.2920
function [A] = Gauss_Elim(A)
t=tiledlayout('flow');
colormap turbo
%Performs Gaussian Elimination%
N = length(A);
tol = 1e-6;
%for each pivot along the diagonal
for ii = 1:N-1
%for each row under the pivot
for jj=ii+1:N
if abs(A(jj,ii)) > tol
%factor is ratio between pivot value
%and entry below pivot in row jj
fac=A(ii,ii)/A(jj,ii);
%row replacement
A(jj,:) = fac*A(jj,:)-A(ii,:);
imagesc(nexttile,A)
clims=get(t.Children,'CLim');
if iscell(clims)
clims=cell2mat(get(t.Children,'CLim'));
end
caxis([min(clims(:,1)) max(clims(:,2))])
drawnow
end
end
end
end

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Nick
Nick 2021-11-2
Yes, sorry I meant to display the matrix A on each iteration. Thank you for the help!

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Image Analyst
Image Analyst 2021-11-3

0 个投票

To show each step (each line of code as it's being executed), you can tell it
echo on
To show A, remove the semicolon from the end of the line.
A(jj,:) = fac*A(jj,:)-A(ii,:)

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