MATLAB: Search a Table With Numerical Entries

create tablesearch table

I have a table which has only numerical (actually integer) entries. Each row and column are indexed by a string. As an example,
I1L I1R I2L I2R I3 I4
—– —– —– —– —– —–
I1L 0 0 2 0 1 0
I1R 0 0 0 1 1 0
I2L 10 0 0 3 0 0
I want to be able to identify the non-zero entries and then create a 3-column table which has the row name, column name, and the integer value. For example,
I1L I2L 2
I1L I3 1
I1R I2R 1
I1R I3 1
I2L I1L 10
I2L I2R 3
Of course, the table that I am working with is quite large. I have been trying various combinations of commands, all in vain I'm afraid. I would very much appreciate any assistance. Thank you.

Best Answer

If you want to make a digraph from your table, you don't need to go to the three-column table first. Let's make a sample table in the same form as what you have. Let's start off with 20 non-zero values at random locations in a 10-by-10 array.
ind = randi(100, 1, 20);
weight = randi(10, 1, 20);
A = zeros(10, 10);
A(ind) = weight;
Turn this into a table array with variable names A1, A2, ... [Yes, I know defining stand-alone variables with numbered names is discouraged. Letting MATLAB automatically make variables inside a table array with numbered names like this doesn't clutter the namespace, so I'm okay with that.]
T = array2table(A)
Now build your digraph. I assumed you want the node names in the digraph to be the variable names in the table.
D = digraph(T.Variables, T.Properties.VariableNames)
If you only wanted some of the rows and variables to be present:
selection = 1:2:width(T);
D2 = digraph(T{selection, selection}, T.Properties.VariableNames(selection))