I have a structure (data) which consist of 322 cells a 296(features)*2000(timepoints). I want a matrix per timepoint which consists of trials^features^timepoints (322 *296*2000). What I am currently doing and what also works fine is using a for-loop:
for k=1:size(data.trial{1,1},2)
for i= 1:length(data.trialinfo)
between=data.trial{1,i}';
data(i,:,k)=between(k,:);
end
end
Can anyone think of a faster way to do that? Because it takes ages as the matrix increases.
Thanks!
Carlos
Try:
data2 = permute(reshape([data.trial{:}],296,2000,322),[3,1,2]);
The issue with reshape is that it thinks in columns, so you need to permute afterwords (ie. 3D transpose), since that's how you set up the output variable in your loop. I used concatenation instead of cell2mat for speed.
I assumed this worked as sample data:
for ii= 1:322
data.trial{1,ii} = rand(296,2000);
end
Related
I have this program which calculates the realized covariance for each day in my sample but I have some troubles with storing the output in a matrix.
the program is as follows:
for i=1:66:(2071*66)
vec = realized_covariance(datapa(i:i+65),data(i:i+65),datapo(i:i+65),data(i:i+65),'wall','Fixed',fixedInterval,5)
mat(2,4142) = vec
end
Output:
vec =
1.0e-03 *
0.1353 -0.0283
-0.0283 0.0185
Subscripted assignment dimension mismatch.
I have tried various way to store the output in a matrix like defining a matrix on zeroes to store the output in or let the row dimension of the storing matrix be undefined, but nothing seems to do the job.
I would really appreciate an advice on how to tackle this challenge.
I have used a solution which does the job.
I defined a matrix and then filled in all my output one at the time using the following:
A = zeros(0,0) %before loop, only serve to define the storing matrix
A = [A; vec]%after the calculating function, inside the loop.
Actually mat(2,4142) is a single location in a matrix, you can't assign there four values.
You need to define the exact location inside mat every time you want to assign values into it. Try doing it like that:
mat=zeros(2,2142);
for k=1:66:(2071*66)
vec=realized_covariance(datapa(i:i+65),data(i:i+65),datapo(i:i+65),data(i:i+65),'wall','Fixed',fixedInterval,5)
mat(:,[(((k-1)/66)*2)+1 (((k-1)/66)*2)+2])=vec;
end
You're trying to store a 2 x 2 matrix into a single element. I.e. 4 elements on the right hand side, one on the left. That won't fit. See it like this: you have a garage besides your house where 1 car fits. You've got three friends coming over and they also want to park their car inside. That's a problem though, as you've got only space for one. So you have to buy a bigger garage: assign 4 elements on the left (e.g. mat(ii:ii+1,jj:jj+1) = [1 2;3 4]), or use a cell/structure array.
As Steve suggests in a comment below, you can use a 3D matrix quite easily:
counters = 1:66:(2071*66);
mat = zeros(2,2,numel(counters)); %// initialise output matrix
for ii=1:numel(counters)
vec = realized_covariance(datapa(counters(ii):counters(ii+65)),...
data(counters(ii):counters(ii+65)),datapo(counters(ii):counters(ii+65)),...
data(counters(ii):counters(ii+65)),'wall','Fixed',fixedInterval,5)
mat(:,:,ii) = vec; %// store in a 3D matrix
end
Now mat is 3D, with the first two coordinates being your regular output, i.e.e vec, and the last index is the iteration number. So to access the output of iteration 1032 you'd do mat(:,:,1032), possibly with a squeeze around that to make it 2D instead of 3D.
I have matchcounts (5x5)cell, every cell has a vector of double [106x1]. The vectors of double have zeros and non zero values. I want to find non zero values for every cell, count them and put the result in a matrix.
I tried with this code:
a{i,j}(k,1)=[];
for k=1:106
for i=1:5
for j=1:5
if (matchcounts{i,j}(k,1))~=0
a{i,j}=a{i,j}(k,1)+1;
end
end
end
end
and others but it's not correct! Can you help me? Thanks
While it is possible to fix your answer above, I recommend to change the data structure to have a much simpler solution possible. Instead of having a 2D cell array which holds 1D data, choose a single 3D data structure.
For an optimal solution you would change your previous code code to directly write the 3D-matrix, instead of converting it. To get started, this code converts it so you can already see how the data structure should look like:
%convert to matrix
for idx=1:numel(matchcounts)
matchcounts{idx}=permute(matchcounts{idx},[3,2,1]);
end
matchcounts=cell2mat(matchcounts);
And finding the nonzero elements:
a=(matchcounts~=0)
To index the result, instead of a{k,l}(m,1) you use a(k,l,m)
To give you some rule to avoid complicated data structures in the future. Use cell arrays only for string data and data of different size. Whenever you have a cell array which contains only vectors or matrices of the same size, it should be a multidimensional matrix.
I have a problem with the following code. I want to store all the values I am creating in the for loop below so that I can make a plot of it. I have tried several things, but nothing works. Does anyone know a simple method to create a vector of the results and then plot them?
dx=0.1;
t=1;
e=1;
for x=-1:dx:1
lower_bound=-100;
upper_bound=x/(sqrt(4*t*e));
e=1;
u=(1/sqrt(pi))*quad(#integ,lower_bound,upper_bound);
plot(x,u)
hold on
end
hold off
I would like to use as much of this matlab code as possible.
dx=0.1;
t=1;
e=1;
xval=[-1:dx:1].';
upper_bound = zeros(numel(xval),1);
u = zeros(numel(xval),1);
for ii=1:numel(xval)
x = xval(ii)
lower_bound=-100;
upper_bound(ii,1)=x/(sqrt(4*t*e));
u(ii,1)=(1/sqrt(pi))*quad(#integ,lower_bound,upper_bound(ii));
end
figure;
plot(xval,u)
by adding the (ii) behind your statements it saves your variables in an array. I did not use that on your lower_bound since it is a constant.
Note that I first created an array xval and called that with integers in ii, since subscriptindices must be positive integers in MATLAB. I also initialised both upper_bound and u by creating a zero matrix before the loop executes. This is handy since extending an existing vector is very memory and time consuming in MATLAB and since you know how big they will get (same number of elements as xval) you might as well use that.
I also got the plot call outside the loop, to prevent you from plotting 21 blue lines in 1 plot.
I have a 3D large Matrix, the first index (x) represents frequency and the second and third indexes (y and z) are the indexes of the data. I want to print the data for each index for all the frequencies, then print a | char and a new line char. I do this in the following way:
% S is a 3D matrix of size (x,y,z), where y=z and x>>y
N=size(S,2);
MM=real(S);
for mi=1:N
for mj=1:N
fprintf(fid,"%.16g ",MM(:,mi,mj));
fprintf(fid,"|\n");
end
end
But for large matrices this is very slow. Is there a way to speed up the process?
This is done in octave, which means that a Matlab solution will work as well.
If I understood your input data correct, your loop is equivalent to:
fprintf(fid,[repmat('%.16g ',1,size(S,1)) '|\n'],permute(real(S),[1,3,2]));
fprintf starts over using the format string when it reaches the end. The permute is necessary to preserve the order from your code.
Here is a general approach to speed things up:
Calculate everything you want to calculate, store each result as a number or a string
Print the result to file in 1 go
m=zeros(3,4,5);
[x,y,z]=size(m);
for k=1:x
for l=1:y
dlmwrite('D:\test.txt',m(k,l,:),'-append','delimiter',' ','newline','pc');
end
dlmwrite('D:\test.txt',[' '],'-append','newline','pc');
end
I am a total beginner in MATLAB and I hope to find some help here. I have some model prediction results for 80 individuals alltogether in one large matrix. I need to extract the data for each individual from the big matrix, assign them in a new variable/matrix, do some extra calculations and then plot certain information as needed.
To do so, I am trying to write a script with a loop function but in a complicated, or maybe more accurately: in a primitive way!
Simplified Example:
My matrix is called: All_Indi_Data .... its dimension is: 600 rows x 21 columns
%Column 1: grouping variable (e.g., code or ID with values 1,2,3,4,5, etc.);
%Column 2: independent var.;
%Column 3: t;
%Column 4: OBS;
%Column 5: PRED;
i= length (All_Indi_Data);
%% First Indi.
q=1; % indicating the ID of the indi for which I want to extract the data
j=1; % variable added to insure writing start from the first row
for r=1:i
if All_Indi_Data (r,1)==q
Indi_1 (j,1:21) = All_Indi_Data (r,1:21)
j=j+1
end
end
%% Second Indi.
q=q+1
j=1
for r=1:i
if All_Indi_Data (r,1)==q
Indi_2 (j,1:21) = All_Indi_Data (r,1:21)
j=j+1
end
end
.
.
.
1) My first question is: can I allocate these data in new variables (Indi_1, Indi_2, ect.) in a more simple way with or without the loop function?!!! I would appreciate your help a lot.
2) Is there any code or any way to plot these selected parts (according to the grouping variable, e.g. data for Indi_1) from the previously mentioned big matrix without wasting a lot of time and space (wto recopying the core part of the code again and again) for the script, and using the loop function?! in other words, I would like to detect - with loop function & the grouping variable- which values are of interest and then to plot them (e.g. data in colum 3 with data from column 4 for each individual, starting from the first to the last)?!
I hope that I described my problem clearly and hope to hear something from the expert guys :) ...
Thanks a lot in advance ..
Try the following code:
for idx=1:80
pos=find(All_Indi_Data(:,1)==idx);
eval(['Indi_' num2str(idx) '=All_Indi_Data(pos,:);']);
end
What I do is: in each iteration, I search for a value of the ID, indicated in the variable idx. Note that I do not use ´i´ as the name of a variable, because Matlab uses it and ´j´ and the imaginary unit for complex numbers and that could cause problems.
Then, using find I search for the position (or positions) of All_Indi_Data in which I can find the information of that individual. Now I have in the variable ´pos´ the indexes of the rows in which there is information for the individual of interest.
Finally, using eval I extract the data for each individual into a variable. Note that eval combined with a loop makes it easy to create lots of variables. I indicate the rows I want to extract with ´pos´ and, as I want all the columns, I use just ´:´ (you could use ´1:21´ too).
With another similar loop you can plot the information you want. For example:
for idx=1:80
eval(['x=Indi_' num2str(idx) ';']);
% Now I have in X the information for this individual
%Plot the columns of x I want
plot(x(:, 3), x(:,4));
pause; %stay here until a press a key
end