Use function eval( )+ function find() - matlab

Question

%%%%%%%%%%%%% 2 - Old %%%%%%%%%%%%%%%%%%%%
I modified the code as suggested by achieve greater efficiency. I have new errors in the code, not being an expert of access to the cell array
for i = first:N_Files
mat{i} = load(files(i).name);
A{i} = mat{1,i};
x{i} = A{:,i};
ind{i} = find(x{i}>= -0.5 & x{i}<=0.5);
% New error
B{i} = A{ind{i,:},:}; **Index exceeds matrix dimensions.**
xx{i} = B(:,1);
end
%%%%%%%%%%%%% 1 - Old %%%%%%%%%%%%%%%%%%%%
I wrote a routine to access files placed in different folders.
Then build a cell array where are stored file data with the routine:
for i = first:N_Files
mat{i} = load(files(i).name); % 1x3 cell
eval(['A' num2str(i) '= mat{1,i} ;']) % A1,A2,A3 dim : 114336x6 double
end
A = {A1, A2, A3}; cell array 1x3
I have a problem of access to some vectors created on the evaluation of a matrix cell.
for i = first:N_Files
eval(['x' num2str(i) '= A{:,i} ;']) % create x1, x2, x3
% incorrect code
eval(['ind' num2str(i) '= find('x' num2str(i) >= -0.5 & 'x' num2str(i)
<=0.5) ;'])
end
% need this indexing solution
ind1 = find(x1>= -0.5 & x1<=0.5);
ind2 = find(x2>= -0.5 & x2<=0.5);
ind3 = find(x3>= -0.5 & x3<=0.5);
I necessity to have the eval function with the find function,
it's possible?
have a useful solution?
thanks
%%%%%%%%%%%%% Complete Code %%%%%%
This is the code that I had to get.
for i = first:N_Files
A{i} = load(files(i).name); % 1x3 cell
x = A{:,1};
ind{i} = find(x(:,1)>= -0.5 & x(:,1)<=0.5); % This looks cleaner
B{i} = A{i}(ind{i},:); % Correct,first access element i in A then filter.
xx{i} = B{i}(:,1); %1x3 cell **what i really wanted**
yy{i} = B{i}(:,2);
zz{i} = B{i}(:,3);
u{i} = B{i}(:,4); % vettore velocità
v{i} = B{i}(:,5);
w{i} = B{i}(:,6);
c1{i} = [-0.5:0.01:0.5];
c2{i} = [0:0.01:2] ;
[X{i},Z{i}] = meshgrid(c1{i},c2{i});
U{i} = griddata(xx{i},zz{i},u{i},X{i},Z{i});
U{i}(isnan(U{i}))=0; % interpolazione ai bordi
W{i} = griddata(xx{i},zz{i},w{i},X{i},Z{i});
W{i}(isnan(W{i}))=0;
figure
pcolor(X{i},Z{i},(U{i}.^2+W{i}.^2).^0.5);
shading(gca,'interp')
title('Velocità')
colorbar;
axis square
hh = streamslice(X{i},Z{i},U{i},W{i});
set(hh,'color','k');
end

Answer 1

Ok I will try to help you as good as I can. First, if you have a cell that have the dimension 1xN, you do only need one index: A{i} = mat{i}. However, you then see that A==mat, which means that both are not needed. On the next row, you do x{i} = A{:,i} which seems to be the same as you do on the former row => x==mat. This means that we can remove two rows. Then I guess that your goal is to find the indices which have an absolute value smaller than 0.5 for each file and store each in a cell, right? Then to the error: By doing A{ind{i,:},:} you are actually sub-referencing A itself and not each element of A. The size of A is 1*nFiles. What you are trying to do is indeed this: B{i} = A{i}(ind{i}).
So if this is not what you want please comment. Otherwise, remove redundant variables. And make sure that you do not mix up cell with matrix. You use a cell as a container for arrays: a{n} refers to the array in cell element n and a{n}(m) refers to matrix element m in the array located in cell element n. Good luck!
for i = first:N_Files
mat{i} = load(files(i).name);
%A{i} = mat{1,i}; % not needed mat==x
%x{i} = A{:,i}; % not needed x==A
x = mat; % Fix this later, I do not want to change any variable names.
% ind{i} = find(x{i}>= -0.5 & x{i}<=0.5);
ind{i} = find(abs(x{i})<=0.5); % This looks cleaner
%B{i} = A{ind{i,:},:}; **Index exceeds matrix dimensions.**
B{i} = A{i}(ind{i}); % Correct,first access element i in A then filter.
xx{i} = B(:,1); %I do not know what you tries to do but probably
%xx{i}=B{i} => x==B so one variable is redundant.
end