Hello!

I would like to ask for your help on how to open a text file in scilab and placing its elements in an array, so that I can plot the elements and calculate its mean-squared displacement.

The data in the text file looks like this:

`===start of file===`

3 1 1 17 2 2 14 1 2 3

`# and so on...`

====end of file====

The data points for the plot look like this: (x-val, y-val) or

[(1,3),(2,1),(3,1),(4,17),(5,2),(6,2),(7,14),(8,1),(9,2),(10,3),...]

where x-val are just counting numbers 1,2,3,4,5,... and y-val are the elements of the input file.

Also, using the same input file, the mean-squared displacement is calculated like this (matlab code):

`===start of matlab codes===`

```
nData = size(data,1); %# number of data points
numberOfdeltaT = floor(nData/4); %# for MSD, dt should be up to 1/4 of number of data points
msd = zeros(numberOfDeltaT,3); %# We'll store [mean, std, n]
%# calculate msd for all deltaT's
for dt = 1:numberOfDeltaT
deltaCoords = data(1+dt:end,2:4) - data(1:end-dt,2:4);
squaredDisplacement = sum(deltaCoords.^2,2); %# dx^2+dy^2+dz^2
msd(dt,1) = mean(squaredDisplacement); %# average
msd(dt,2) = std(squaredDisplacement); %# std
msd(dt,3) = length(squaredDisplacement); %# n
end
```

`====endof matlab codes====`

Given this code, how do we plot msd (y-axis) vs deltaT (x-axis)?

I appreciate all your help. Thank you!

Scilab

Code given below will help you to understand how to import numerical values from a .txt file.

clc;

clear;

a=read('test.txt',-1,1) //read the numbers from .txt file

b=0:length(a);

c=length(a)//length of x and y axes

for i=1:c

x(i)=b(i)+1;

for j=1:c

y(j)=a(j);

end

end

points = list([x y]);

disp(points, "Points are :");

xtitle("Graph name","X-axis", "Y-axis");

plot(x,y);

By using these points, you can calculate the value of MSD further.

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