where is the error?

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gianluca
gianluca 2012-9-17
Hi, running the following script:
% Create a data set:
x = rand(100,1)*4 - 2;
y = rand(100,1)*4 - 2;
S = x.*exp(-x.^2-y.^2) * 1000;
% Construct the interpolant:
F = TriScatteredInterp(x,y,S);
% Evaluate the interpolant at the locations [XI,YI].
XI = -2:0.25:2;
YI = -2:0.1:2;
[XImat,YImat] = meshgrid(XI,YI);
ZImat = F(XImat,YImat);
% Define a set of ZI locations
ZI = -500:100:500;
% Find the node above the surface S
BW = false(length(YI),length(XI),length(ZI));
for i = 1:length(YI)
for j = 1:length(XI)
BW(i,j,:) = ZImat(i,j)<ZI;
end
end
KImat = zeros(size(ZImat));
for i = 1:length(YI)
for j = 1:length(XI)
firstIndex = find(BW(i,j,:),1);
if ~isempty(firstIndex)
KImat(i,j) = firstIndex;
end
end
end
% Create a 3d grid where to compute a value at each node above the surface S
[X,Y,Z] = meshgrid(XI,YI,ZI);
for i = 1:length(YI)
for j = 1:length(XI)
if KImat(i,j) == 1
for i = 1:length(Y)
for j = 1:length(X)
for k = 1:length(Z)
T_geotherm(i,j,k) = 18 + 0.003 .* (Z(i,j,k));
end
end
end
end
end
end
dislay this message: 'Attempted to access Z(1,1,12); index out of bounds because size(Z)=[41,17,11].'
where is the error?
Thanks, Gianluca
  4 个评论
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gianluca
gianluca 2012-9-17
Hi, I cleared the workspace and the message and the variable T_geotherm do not appear. OK, They were an old message and an old variable. Do you have any suggestion how to compute a value at each node of the 3d matrix [X,Y,Z] above the surface S? I hope to be right till the definition of the variable KImat. The last part of the script is wrong
Wayne King
Wayne King 2012-9-17
The variable, T_geotherm, is not being generated because your if statement if KImat(i,j) == 1 is never true

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采纳的回答

Jan
Jan 2012-9-17
编辑：Jan 2012-9-17
Matlab code gets much cleaner and easier to debug, when vectorization is applied:
Ugly and due to a missing pre-allocation slow in addition:
for i = 1:length(Y)
for j = 1:length(X)
for k = 1:length(Z)
T_geotherm(i,j,k) = 18 + 0.003 .* (Z(i,j,k));
end
end
end
Beautiful and fast:
T_geotherm = 18 + 0.003 .* Z;
Btw, using nested loops with the same counter is not really clean, but not an error:
for i = 1:length(YI)
for j = 1:length(XI)
if KImat(i,j) == 1
for i = 1:length(Y)
for j = 1:length(X)
It is strongly recommended to avoid such confusing constructions.
  2 个评论
gianluca
gianluca 2012-9-17
OK, vectorization is better! But I need to define for which nodes and till which nodes along k index compute the variable T_geotherm. The logical matrix BW say me with a zero or an one if the nodes are above or below yhe surface S, KImat say me the first index where it realized. Then, how can I do this? foe example (but it do not work):
for i = 1:length(YI)
for j = 1:length(XI)
if KImat(i,j) >= 1
T_geotherm = 18 + 0.003 .* Z;
end
end
end
Jan
Jan 2012-9-17
编辑：Jan 2012-9-17
index = (KImat >= 1);
T_geotherm(index) = 18 + 0.003 .* Z(index);

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更多回答（1 个）

Wayne King
Wayne King 2012-9-17
I can run this without error. I think you have some variable in your workspace that is conflicting with this and causing the error.
Can I suggest you first clear the workspace and then try to run this script?

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