Matlab : reshaping matrix from a vector - matlab

Question

I've been making a multi-channel steaming DAQ system in Labview.
And, I bring the saved binary file into Matlab for post-processing.
I need to sort the file data, according to channels.
An example is below.
with 3 multiple channel acquisition and 5Hz sampling rate
First channel voltage : 1V(constant)
Second channel voltage : 2V(constant)
Third channel voltage : 3V(constant)
if I acquire signals for 4 seconds with this condition, the saved data will be like below, because the system saves the signal in buffer, once in a second, on a single file.
ch1=[1 1 1 1 1];
ch2=[2 2 2 2 2];
ch3=[3 3 3 3 3];
B=[ch1 ch2 ch3 ch1 ch2 ch3 ch1 ch2 ch3 ch1 ch2 ch3];
I want to rearrange the data like below.
desiredB=[ch1 ch1 ch1 ch1; ch2 ch2 ch2 ch2; ch3 ch3 ch3 ch3];
In order to rearrange B I made a code like below with two for loop.
fs=5; %sampling frequency
nCh=3; %number of channels
nB=length(B);
C=zeros(nB/fs,fs);
for i=1:nB/fs;
temp=B((i-1)*fs+1:fs*i);
C(i,1:fs)=temp;
end
sizeC=size(C);
T=sizeC(1)/nCh;
D=zeros(nCh,fs*T);
for j=1:T
temp2=C(3*(j-1)+1:3*j,:);
D(:,(j-1)*fs+1:j*fs)=temp2;
end
t_axis=0:1/fs:T-1/fs;
plot(t_axis,D','linewidth',2),grid on
axis([0 3.8 0 5])
xlabel('time(sec)')
ylabel('voltage(V)')
legend('first channel','second channel','third channel')
It worked, but when I read a big size data, it's slow.
Are there any nice ways to reshape this kind of data?

Answer 1

I think this does what you want:
fs=5; %sampling frequency
nCh=3; %number of channels
ch1=[11 12 13 14 15];
ch2=[21 22 23 24 25];
ch3=[31 32 33 34 35];
B=[ch1 ch2 ch3 ch1 ch2 ch3 ch1 ch2 ch3 ch1 ch2 ch3];
C = reshape(B, fs, nCh, []);
D = permute(C, [1, 3, 2]);
E = reshape(D, [], nCh).'
E =
11 12 13 14 15 11 12 13 14 15 11 12 13 14 15 11 12 13 14 15
21 22 23 24 25 21 22 23 24 25 21 22 23 24 25 21 22 23 24 25
31 32 33 34 35 31 32 33 34 35 31 32 33 34 35 31 32 33 34 35