Different conditions, matching values

Hi everyone,

I have a matrix with two columns of data. The data in the first column vary from 1 to 120. The data in the second column vary from 1 to 12.

A= [10 114 10 8 111 102 10 102 10].

B= [2 4 5 7 12 2 3 2 1].

I would like to calculate:

i) the number of times an element of column A (cA), between 100-109 is followed by a cA' value < 100 (indicating each of these elements);

ii) the number of times an element of cA > 109, is preceded by a cA' value < 100 (indicating each of these elements).

Additionally, that calculation should respect the elements of column B (cB) that match with the elements of cA >= 100.

For example, an output like this one.

cA cA cB n

114 10 4 1

111 8 1 1

102 10 2 2

How can I do that?

Thanks.

[KALYAN ACHARJYA]

Home Work??

Number of times an element of column A (cA), between 100-109

num_counts=sum(A(:,1)>100 & A(:,1)>109)

Do the similar approach for others, it may be home work, therefore try it and learn

Answer 1

[Neuropragmatist]

I don't really see how the output you give represents what you described in the question, or what you mean by

"that calculation should respect the elements of column B (cB) that match with the elements of cA >= 100"

However, i) and ii) can both be done with logical indexing:

A= [10 114 10 8 111 102 10 102 10];
B= [2 4 5 7 12 2 3 2 1];

% problem i)
idx1 = A>100 & A<109 & [A(2:end) NaN]<100
values = A(idx1)
num_times = sum(idx1)

% problem ii)
idx2 = A>109 & [NaN A(1:end-1)]<100
values = A(idx2)
num_times = sum(idx2)

Hope this helps,

M.