Nested for loop troubles

Hi Everyone,

I am having difficulty troubleshooting a nested for loop. Things work fine on the first pass (when i=49) but break down on the second pass (when i=50). More specifically, instead of appending to consolFut1 on the second pass, it overwrites the data from the first pass. Can anyone spot the error? Thanks for reading.

for i = 49:52
    exp=find(tifDate==expDate(i));
    for j = [1; 18; 43; 63]
        tifCls1 = tifCls(j:exp);
        for k = [1112; 1129; 1154; 1174]
            consolFut1=consolFut(k:expDateIdx(i),i);
            arbTIF=tifCls1-consolFut1;
            break;
        end
    end
end

[James Tursa]

What are the dimensions of your variables? The usual procedure is to pre-allocate an array to contain the outputs from each iteration. I assume the break statement is there for debugging, because as written it will always exit the k loop on the first iteration.

[Cary]

I would be really grateful to anyone who can help me solve this issue. I've spent all day and night trying to fix it. On the second pass, consolFut1 overwrites the column instead of adding to the bottom of it. I don't understand why it does this as tifCls1 works perfectly. Thank you for your time. I sincerely appreciate it.

Answer 1

[Image Analyst]

Nothing on the left hand side of your equations takes an index, so they all get overwritten at each iteration. Add an index if you want to store the different values.

exp is a built in function. Don't use it as the name of a variable!

[Cary]

I'm sorry, I'm having trouble following. Can you clarify a little more for me please?

[Image Analyst]

consolFut1 is a 2D array. Are you trying to append a whole column to the right hand side of it? If so, then do this

consolFut1 = [consolFut1, consolFut(k:expDateIdx(i),i)]

Of course you have to make sure that the number of rows from consolFut (which is different than consolFut1 because there's no 1 at the end of it) that are specified in k:expDateIdx(i) matches the number of rows in consolFut1.

Or you could preallocate consolFut1 and then just assign a column. The thing that worries me is that k and expDateIdx(i) vary with iteration so how can we be certain that the number of rows match? In other words, that length(k:expDateIdx(i)) matches size(consolFut1, 1).

[Cary]

I'm not trying to append to the right. On the first pass the data is stored in consolFut1 (a column). On the second pass, instead of appending to the bottom of the column, it overwrites the data from the beginning. The column should be getting longer and longer with each pass, while keeping the old data.

[Walter Roberson]

consolFut1 = [ consolFut1; consolFut(k:expDateIdx(i), i).' ];

Having multiple elements in the first dimension of the consolFut is for selecting part of a row. If you want those elements to be written into a column then you need to transpose the row to become a column.