Bsxfun extension to account for specific indexes in a matrix

Question

I have a problem. I am trying to implement this short piece of code.

The main steps that I have already taken. Please check my code below:

clc;clear all;close all; A=round(-3+(6).*rand(5,5)); B=round(-3+(6).*rand(5,5)); %//The check matrix stores the conditions present on the right side of the equation. check = A.*B %//upd_max and upd_min are the given as the del_max and del_min in the equation upd_max = 0.5; upd_min = 0.1; %//eta_plus and eta_minus are denoted as nplus and nminus nplus = 1.2; nminus = 0.5; %del_(k-1)_i matrix is given as update_mat update_mat = (0.1+(0.4).*rand(size(check))).*ones(size(check)) update_new = update_mat.*(check==0) + bsxfun(@min,(nplus.*update_mat.*(check>0)),upd_max)... + bsxfun(@max,nminus.*(update_mat.*(check<0)),upd_min) 

I have provided below a sample result of my piece of code:

 check = 2 -6 0 -1 2 -3 -4 3 -3 4 0 2 -2 6 0 2 -1 -4 -1 -3 -2 -4 -3 0 6 update_mat = 0.4102 0.4173 0.1126 0.2268 0.4964 0.4622 0.3750 0.4282 0.3422 0.1495 0.4760 0.3820 0.2903 0.3143 0.1473 0.3603 0.2861 0.3122 0.3527 0.2908 0.3602 0.3696 0.3220 0.2046 0.4746 update_new = 0.5922 0.2087 0.2126 0.1134 0.6000 0.2311 0.1875 0.6000 0.1711 0.2794 0.5760 0.5584 0.1452 0.4772 0.2473 0.5324 0.1431 0.1561 0.1763 0.1454 0.1801 0.1848 0.1610 0.3046 0.6000 

However, this answer is incorrect !! To explain, I divide my answer into three parts:

 update_mat.*(check==0) ans = 0 0 0.1126 0 0 0 0 0 0 0 0.4760 0 0 0 0.1473 0 0 0 0 0 0 0 0 0.2046 0 bsxfun(@min,(nplus.*update_mat.*(check>0)),upd_max) ans = 0.4922 0 0 0 0.5000 0 0 0.5000 0 0.1794 0 0.4584 0 0.3772 0 0.4324 0 0 0 0 0 0 0 0 0.5000 

As you can see, the first two members are correct . However, the third term is incorrect. The third term comes as follows:

 bsxfun(@max,nminus.*(update_mat.*(check<0)),upd_min) ans = 0.1000 0.2087 0.1000 0.1134 0.1000 0.2311 0.1875 0.1000 0.1711 0.1000 0.1000 0.1000 0.1452 0.1000 0.1000 0.1000 0.1431 0.1561 0.1763 0.1454 0.1801 0.1848 0.1610 0.1000 0.1000 

The right third term should give me

  0 0.2087 0 0.1134 0 0.2311 0.1875 0 0.1711 0 0 0 0.1452 0 0 0 0.1431 0.1561 0.1763 0 0.1801 0.1848 0.1610 0 0.1000 

I want bsxfun to calculate the wise maximum element only for nonzero elements of the nminus.*(update_mat.*(check<0)) Matrix nminus.*(update_mat.*(check<0)) , and not for all matrices. Can this be done?

Thanks in advance! PS: Please give ideas for better optimized code.

Answer 1

You do not need bsxfun, since you are dealing with a scalar, you just need logical indexing:

  M=nminus.*(update_mat.*(check<0)) M((~~M) & (M < upd_min)) = upd_min %// ~~M is the same as M~=0 

(btw this assumes that for your example data you made a mistake in the second last row of the last column where you have 0 , but I think you want 0.1454 )