Question

Once again, sorry if this has been asked before and if its too specific but I’m very stuck and can’t quite find a solution.

I have a matrix of say 3 members of a structure called 2, 4 and 16 (in column 1) that have values along their relative distance e.g. member 2 has values at the start, 0m, then at 0.5m then the end of its length 1.5m, where member 4 starts at 0m etc. So that my matrix looks like this:

2   0     125
2   0.5   25
2   1.5   365
4   0     25
4   0.6   57
16  0     354
16  0.2   95
16  0.8   2

and I want to create a matrix that has the overall distance along all the members 2, 4 and 16 combined:

2   0     125
2   0.5   25
2   1.5   365
4   1.5   25
4   2.1   57
16  2.1   354
16  2.3   95
16  3.1   2

is there any way to do this in matlab? Like possibly locating the first zero and adding the value above it to all the rest of the values below then find the next zero value and so on?

Please tell me if this isn’t clear, I realise it’s a bit confusing but not too sure how to explain it better!

Answer 1

I came up with the following:

idx = find(diff(M(:,1)));
v = zeros(size(M,1),1);
v(idx+1) = M(idx,2);
M(:,2) = M(:,2) + cumsum(v);

The result:

M =
            2            0          125
            2          0.5           25
            2          1.5          365
            4          1.5           25
            4          2.1           57
           16          2.1          354
           16          2.3           95
           16          2.9            2

Note the last value in the second column disagrees with what you described (2.9 vs 3.1). Either you had a typo, or I’m still not getting it…