Matlab cross referencing matrix and table elements

[hoffmann]

hi all, here's an interesting problem I've been working on in MATLAB. any help would be appreciated.

i have four column vectors of length ~11000 (table1):

in1 in2 out1 out2
11 4 101 47
1 8 111 9
38 1 1 39
...

i also have a matrix with dimensions 111x111 (matrix1):

c1 c2 c3 c4 ...
c1 0 0 0 1
c2 0 0 1 1
c3 0 1 0 0
c4 1 1 0 0
...

the first four column vectors in table1 represent reactions (read across columns) in which compounds 1 through 111 can participate in. compound 1 in table1 represents a compound with zero mass, so essentially a nonexistent compound. e.g. 11+4=101+47 is the reaction contained in the first row of table 1.

the first reaction in table1 can be classified as A+B=C+D with six possible interactions between the compounds: A-B, A-C, A-D, B-C, B-D, C-D. the second reaction can be classified as A=C+D with its 3 appropriate interactions. the third reaction can be classified as A=D with its 1 interaction.

i basically would like to add 6 more columns to table1 denoting whether an interaction existing in the reaction exists in matrix1. put a 1 in the column when an interaction exists and a 0 otherwise. i need to do this for all reactions in table1. the values in table1 denote the indices of the compounds which should correspond to the row and column labels in matrix1 (i basically added a 'c' tag in front for readability).

i'm having difficulty coding this problem. i would approach it using something like:
for i=1:length(in1)
if matrix1(A,B)==1 && table1(A,B)~=0 %here's where it gets iffy for me
% I'm unsure on how to create columns and make sure i am cross referencing the %elements of table1 and matrix1 properly.

i would appreciate any help since I've tried to conceptualize this problem and believe i am doing so correctly. any more efficient methodologies would be welcome. thanks!

 

[MATLABdude]

I'm not so sure about efficient, but oh well. One way of doing this would be to create a new 2D matrix called table2 using the zeros instruction:

>> table2=zeros(111, 10);

or, if you were looking for more expandability:

>> table2=zeros((size(table1))(1),(size(table1))(2)+4);

and then copy over table1 to table2:

>> table2(1:111, 1:6) = table1

I'm unaware of any function that allows you to EASILY tack on extra columns (I suppose you could transpose, add some rows by putting zeros in the new rows, and then transpose back) but the following Mathworks Matlab documentation page may nevertheless be of some benefit to you (Resizing and reshaping matrices):

http://www.mathworks.com/access/helpdesk/help/techdoc/matlab_prog/f1-85766.html

 

[oswaler]

It seems like you are trying to find a way to cross reference the elements in your table with the elements in your matrix. One way to do this is to use the "ismember" function in MATLAB. This function allows you to check if an element in one array is present in another array and returns a logical value (1 if present, 0 if not present).

In your case, you could use the "ismember" function to check if the values in your table correspond to the row and column labels in your matrix. For example, for the first reaction in your table (11+4=101+47), you could use the "ismember" function to check if the values 11, 4, 101, and 47 are present in the row and column labels of your matrix. This would give you a logical array with values [1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, ...] which you could then add as additional columns to your table.

You may also want to consider using a different data structure, such as a cell array or a structure, to better organize your data and make it easier to access and manipulate. You could also consider using a "for" loop to iterate through each reaction in your table and use the "ismember" function to check for the presence of interactions in your matrix.

Overall, there are several approaches you could take to solve this problem and it would depend on your specific needs and preferences. I would suggest experimenting with different methods and seeing which one works best for your data and your coding style.