I am doing a project in matlab,first time using it,and our prof sent us this code,can someone explain to me what thats doing? Thank you.

function [Vout, t] = stackoutput(lb, ub, cost1)

n= size(cost1);
n1= n(1);
n1b= n(2);
Vout= zeros(n1,n1b);
t=1;

for i=1:n1
    
    if(cost1(i,1)>= lb && cost1(i,1)<= ub)
        Vout(t,:)=cost1(i,:);
        t=t+1;
    end
    
end

t= t-1;

end

Answer 1

[DGM]

Without context, I doubt anyone can tell you anything more than a literal reading of the code. This is why documentation (a synopsis or at least a single comment) is important. Whoever gave you a bunch of undescribed code is the person to ask.

Buuut I guess nobody likes climbing that hill. Let's add some comments to this thing.

function [Vout, t] = stackoutput(lb, ub, cost1)
% [Vout t] = stackedoutput(lowerbound,upperbound,cost)
%   This function does a thing that is so unimportant that
%   it's not even worth writing a single word in description.
%
% LOWERBOUND is a numeric scalar
% UPPERBOUND is a numeric scalar
% COST is a numeric matrix (2D)
% 
% VOUT is a numeric matrix containing the rows from COST where
%    the first column falls between LOWERBOUND and UPPERBOUND
% T is a numeric scalar representing the number of valid rows in VOUT

n= size(cost1);
n1= n(1);
n1b= n(2);
Vout= zeros(n1,n1b); % initialize Vout to be same size as cost1

t=1; % output row index starts at one
for i=1:n1 % step row by row
    
    % if first element of this row is within bounds
    if(cost1(i,1)>= lb && cost1(i,1)<= ub)
        % then cram that row into the output array on row t
        Vout(t,:)=cost1(i,:);
        % and increment the output row index
        t=t+1;
    end
    
end
% since this index is used as a counter and we started at 1 instead of zero
% we have to subtract one to have a correct count of valid rows
t= t-1;
end

This whole mess with loops can be replaced:

function [Vout, numvalidlines] = stackedthing2(lowerbound,upperbound,cost)
% synopsis goes here

[h w] = size(cost);
Vout = zeros(h,w);

inbound = (cost(:,1) >= lowerbound) & (cost(:,1)<= upperbound);
numvalidlines = nnz(inbound);
Vout(1:numvalidlines,:) = cost(inbound,:);
end

Since there's zero context provided, it's not clear whether the output array is ideally supposed to have a bunch of extra empty rows. If not, the answer can be simplified further yet.

function [Vout, numvalidlines] = stackedthing3(lowerbound,upperbound,cost)
% synopsis goes here
% same thing, but without extra empty rows

inbound = (cost(:,1) >= lowerbound) & (cost(:,1)<= upperbound);
Vout = cost(inbound,:);
numvalidlines = size(Vout,1);
end