When using Eigen in our projects, I found that some useful functions are still missing in the current version of the library.

In particular, we often need to do things to get/set part of an array/matrix like the following (in MATLAB syntax),

idx = [1 3 4 5 8];
b = A(idx); % get a part specified by an index array
A(idx) = ...; % set a part specified by an index array

% get/set a part of a matrix, whose rows and columns are specified by
an array of indices

irows = ...;
icols = ...;
A(irows, icols) = ...;
B = A(irows, icols);

% indexing using logical (bool) type

A(A > 0) = ...;
B = A(A < 0);

Currently, we workaround this by implementing my own routines, such as get_coeffs, get_rows, get_cols ...

But we would like to see such useful interfaces be supported by Eigen. Are there any plan to provide in upcoming versions?

Thanks.

this feature has been requested many times... just need someone brave enough to implement it!