Loop code for many data files and save

I wrote this code, which load a file text2.dat, to use its data to calculate velocity.

I have many files text3.dat test4.dat...

I want to make this code to load all files and calculate velocity for each file, then save it separatly (vel1.dat, vel2.dat, vel3.dat....)

data=load('test2.dat');
time= data(:,1);
x= data(:,2);
y= data(:,3);
x=x*(3e-7);
y=y*(3e-7);
Vx = gradient(x, time);
Vy = gradient(y, time);
for i=1:n-1
   vel_x(i) = ((x(i)-x(i+1)))/(time(i)-time(i+1));
   %t(i)= x(i)-x(i+1);
   %s= gradient (x);
   vel_y(i) = ((y(i)-y(i+1)))/(time(i)-time(i+1));
   vel(i)   = sqrt(vel_x(i)*vel_x(i)+ vel_y(i)* vel_y(i))
   V(i)  = sqrt(Vx(i)^2 + Vy(i)^2); 
end
%V=V';
indices = find(abs(vel)>2e-4);
vel(indices) = [];
V=V';

Answer 1

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

[Tesla]

thank you this is how to load sequentially numbered files.

But how Can I apply my calculation for every file? and save them sequentially too

[Walter Roberson]

numfiles = 83;           %adjust as needed

for K = 1 : numfiles
    infilename = sprintf('test%d.dat', K);
    outfilename = sprintf('vel%d.dat', K);
    data = load(infilename);
    time= data(:,1);
    x= data(:,2);
    y= data(:,3);
    x=x*(3e-7);
    y=y*(3e-7);
    Vx = gradient(x, time);
    Vy = gradient(y, time);
    for i=1:n-1
       vel_x(i) = ((x(i)-x(i+1)))/(time(i)-time(i+1));
       %t(i)= x(i)-x(i+1);
       %s= gradient (x);
       vel_y(i) = ((y(i)-y(i+1)))/(time(i)-time(i+1));
       vel(i)   = sqrt(vel_x(i)*vel_x(i)+ vel_y(i)* vel_y(i))
       V(i)  = sqrt(Vx(i)^2 + Vy(i)^2); 
    end
    %V=V';
    indices = find(abs(vel)>2e-4);
    vel(indices) = [];
    V=V';
    save(outfilename, 'vel', '-ascii', '-double');
    save(outfilename, V, '-ascii', '-double', '-append')
end

[Tesla]

Thank you very much it works!

Just one thing, I want to add the Time colum in the output file

I tried with

vel = transpose(vel);
save(outfilename,'time' 'vel', '-ascii', '-double');

but didn't work

[Walter Roberson]

you missed a comma after 'time'

[Walter Roberson]

You are deleting some of the vel entries. Remember to delete the corresponding time entries.

You should probably make a variable that has time in the first column and vel in the second column, and save that.

[Tesla]

I see, indeed you are right.

But when I make the loop

for i=1:n

I got this error

Error in veloc (line 16)

vel_x(i) = ((x(i)-x(i+1)))/(time(i)-time(i+1));

For the variable I tried doing something like this:

    A=[time x y vel];

But I got this

Error using horzcat

Dimensions of matrices being concatenated are not consistent.

Error in veloc (line 25)

A=[time x y vel];