how to change axis of a matix?

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my matrix is M(x,y,z) where:
x=1:90
y=1:3:120
z=1:40
and
c=y./z
and I need to convert M into N(x,c).
Any ideas?
  6 个评论
Asliddin Komilov
Asliddin Komilov 2019-9-14
I also suspect that length(c)=y*z, still need to know how to do it.
Walter Roberson
Walter Roberson 2019-9-14
No, length of y and z are the same and y./z would have the same length.
Some of what you wrote does not seem to make sense until you start talking about grids of data, but then you have to ask about the sizes of the grids.

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采纳的回答

Bruno Luong
Bruno Luong 2019-9-15
编辑:Bruno Luong 2019-9-15
load('testdata.mat');
Ufun = @(X,Y,Z) X;
Vfun = @(X,Y,Z) Y./(Z+200);
[X,Y,Z] = ndgrid(x,y,z);
U = Ufun(X,Y,Z);
V = Vfun(X,Y,Z);
U = U(:);
V = V(:);
[umin,umax] = bounds(U);
nu = 21;
u = linspace(umin,umax,nu);
[vmin,vmax] = bounds(V);
nv = 21;
v = linspace(vmin,vmax,nv);
[~,~,I] = histcounts(U,u);
[~,~,J] = histcounts(V,v);
N = accumarray([J I], M(:), [nu nv]-1, @mean, NaN);
midfun = @(x) 0.5*(x(1:end-1)+x(2:end));
u = midfun(u);
v = midfun(v);
surf(u,v,N);
xlabel('u (=x)');
ylabel('v (=y/(200+z)');
mapping3D.png

更多回答(1 个)

Walter Roberson
Walter Roberson 2019-9-14
[X, Y, Z]=ndgrid(1:90,1:3:120,1:40);
C = round(ceil(Y./Z));
N = accumarray([X(:), C(:)], M(:), [], @mean, nan);
surf(N, 'edgecolor', 'none')
xlabel('x')
ylabel('c')
Or possibly N.' instead of N
  8 个评论
Asliddin Komilov
Asliddin Komilov 2019-9-15
I may use C=((y-z)./y); main thing is to obtain the value of M at x by some ratio of y and z, so I can make surface out of it.
Walter Roberson
Walter Roberson 2019-9-15
(y-z)/y is 1-z/y and since z and y both include 0, you still have nan and infinities.

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