# Mean of matrices calculation

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Tahereh Goorangi on 28 Apr 2020
Commented: darova on 11 May 2020
I have 200 .vec files which represent 200 time instances. In each file I have a matrix 'u', velocity, which is 79by49 matrix. I need to find the time average velocity field. Therefore I need to find the average of all the u matrices of all the 200 time instances.
How can I find the mean of all 200, 79by49 u matrices in form of a new 79by49 matrix ?
I would appreciate any suggestions.
Here is my code so far.
thank you,
Tara
clear all % clears all the variables which were open from prev. tasks
clc % clears all the previous commands
close all
files = dir('*.vec');
I = 79;
J = 49;
ScaleFactor = 5.09475; %px/mm
dt = 50e-6; %sec
Fs = 1000; %Hz
tf = 0.2; % 0.2s is the toal time taken to obtain the data for all datapoints ;
ti = 0.001; % is time between two data files
t = ti:ti:tf; % describes the full time taken to capture all the 200 files including time intervals
b1 = 153.6876; % length of the plain cylinder
b2 = 153.6876; % length of the stepped cylinder
u1 = zeros(200,1); % introducing a 200by1 matrix for all the u results at location 1(mid-span)
u2 = zeros(200,1); % introducing a 200by1 matrix for all the u results at location 2(b1/4 above mid-span)
u3 = zeros(200,1); % introducing a 200by1 matrix for all the u results at location 3(b1/4 below mid-span)
v1 = zeros(200,1); % introducing a 200by1 matrix for all the v results at location 1(mid-span)
v2 = zeros(200,1); % introducing a 200by1 matrix for all the v results at location 2(b1/4 above mid-span)
v3 = zeros(200,1); % introducing a 200by1 matrix for all the v results at location 3(b1/4 below mid-span)
for p = 1:length(files)
data_vec = dlmread(files(p).name, ',',1,0);
cntr = 1;
K = 1;
L = 1;
x_grid = (data_vec(1:I,1))/ScaleFactor; %mm
y_grid = (data_vec(1:I:end,2))/ScaleFactor; %mm
u = zeros(I,J);
v = zeros(I,J);
while L<=J
u(K,L) = data_vec(cntr,4)/(ScaleFactor*dt*1000); %m/s
v(K,L) = data_vec(cntr,3)/(ScaleFactor*dt*1000); %m/s
cntr = cntr+1;
K = K+1;
if K-1 == I
K = 1;
L = L+1;
end
end
u1(p) = u(16,24); % to save all the u(16,24) or u at location 1 in the u1 matrix
u2(p) = u(16,12); % to save all the u(16,12) or u at location 2 in the u2 matrix
u3(p) = u(16,36); % to save all the u(16,36) or u at location 3 in the u3 matrix
v1(p) = v(16,24); % to save all the v(16,24) or v at location 1 in the v1 matrix
v2(p) = v(16,12); % to save all the v(16,12) or v at location 2 in the v2 matrix
v3(p) = v(16,36); % to save all the v(16,36) or v at location 3 in the v3 matrix
[x,y] = meshgrid(x_grid,y_grid);
x = x';
y = y';
end
darova on 11 May 2020
you are welcome

Sai Sri Pathuri on 5 May 2020
Hi,
You can find the sum of all velocity matrices and find the average as
% average = (velocityMatrix1 + velocityMatrix2 + ... + velocityMatrix200)/200;
To find the sum and mean of velocity matrices, you may use for loop as mentioned by darova
sum = 0;
for i = 1:200
% load the file corresponding to ith time instant. You may uncomment below code if your files are named u1.vec, u2.vec, ... and so on
% filename = append("u",string(i),".vec");
sum = sum + u;
end
average = sum/200;
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Tahereh Goorangi on 11 May 2020
Hello there,
Thank you so much for the reply.