Why won't this for loop move to the next variable?

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Cary
Cary 2015-6-30
评论： Star Strider 2015-6-30
On the first pass, everything is fine. i = 49, j = 1, k = 1112. On the second pass, i and j move to the next variables (50 and 18), but k stays at 1112. It does the same thing on the third and fourth pass. Can someone please point out my error? My sincerest gratitude for reading.
for i = 49:52
expiry=find(vifDate==expDate(i));
for j = [1; 18; 43; 63]
vifCls1 = vifCls(j:expiry);
for k = [1112; 1129; 1154; 1174]
consolFut1 = consolFut(k:expDateIdx(i),i);
arbVIF=vifCls1-consolFut1;
end
end
end

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回答（2 个）

Thorsten
Thorsten 2015-6-30
编辑：Thorsten 2015-6-30
I you code only i cycles to the values 49,50, ..., while j and k are always a 4x1 vector [1; 18; 43; 63] and k = [1112; 1129; 1154; 1174]. You have to use row vectors in the for loop:
for j = [1 18 43 63]
% some code
for k = [1112 1129 1154 1174]
Star Strider
Star Strider 2015-6-30
Your loops probably are incrementing, but because of the way you created your indices, you’re just not seeing it.
Consider:
ix = 1;
for i = 49:52
for j = [1; 18; 43; 63]'
for k = [1112; 1129; 1154; 1174]'
Q(ix,:) = [i j k];
ix = i + 1;
end
end
end
figure(1)
stem3(Q(:,1), Q(:,2), Q(:,3))
grid on
xlabel('i')
ylabel('j')
zlabel('k')
The plot shows that all the loops are incrementing.
  2 个评论
Thorsten
Thorsten 2015-6-30
编辑：Thorsten 2015-6-30
Your example works because you use row vectors for the indices (or transposed column vectors, to be more precise). Cary's code does not work, because she uses column vectors; it is not a matter of "not seeing it".
Star Strider
Star Strider 2015-6-30
The column vectors quite definitely do not work (that I found surprising).
I transposed them to demonstrate that even if the loops would increment, it will be difficult to see the result because of the inefficient ways the loops are indexed.

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