Please how i can set the indexes of a vector or matrix in Matlab (exactly like the function set index in python)

I have a csv file which has 2 columns and I want to put the first column as an index so that I can synchronize it with another file. Please Please if anyone has any idea how to do it on matlab

[David Hill]

More description would help along with an example csv file. Do you want the values in column 2 stored at the index in column 1? What about the values of other indexes that are not listed in column 1? Will they be zero or nan?

[Inouss]

suppose my csv file is like this:

we call it matrix A

cl1 cl2

12 45

13 46

15 56

34 66

23 60

34 49

Matlab's indexes begin with (1, 2, 3 ....) so I want to change these (1,2, 3) by the elements of column 1 (cl1). So I want to change these (1,2, 3) by the elements of column 1 (cl1). So instead of the first index being 1 I want to replace it by 12 and the 2 by 13, the 3 by 15 .... etc

once done I will delete column 1.

I do not know if it's clear

[Luna]

Can you share as attachment an example of both csv's and the columns you want to synchronize. You may use tables for that. Tables can easily be synchronized with time column or joined with key variables.

[Inouss]

Yes Luna that's it , I join my csv files examples , I want to synchronized chan1 and chan2. The first column is a time columns

[Luna]

Is first column miliseconds? It goes like that:

1303132929

1303132930

1303132931

1303132932

Also how do you want to synchronize or resample these 2 tables? How do you want to fill your missing values? Do you have sampling rate?

Answer 1

[Luna]

Hello,

I wrote some codes for you and I am going to share some links so that you can read in documentation and it will help.

table

timetable

table2timetable

synchronize

Please read my comments below:

chan1_table = readtable('chan1.csv'); % read table 1. Your files must be in your work folder, otherwise use full path name.(Ex: 'C:/Users/.../chan1.csv')
chan2_table = readtable('chan2.csv'); % read table 2
% your both table have Var1 and Var2 variables. Var1 variables are your
% time column.

chan1_table.Var1 = milliseconds(chan1_table.Var1); % convert Var1 into milliseconds. You can use seconds, minutes or any other duration functions.
chan2_table.Var1 = milliseconds(chan2_table.Var1); % same as chan1_table.

%% convert both tables to time table according to their time column. 
TT1 = table2timetable(chan1_table,'RowTimes','Var1'); 
TT2 = table2timetable(chan2_table,'RowTimes','Var1');

%% choose a time step
dt = milliseconds(1); % I choose 1 milliseconds because I don't know what it is. You can change as you wish.
% For example: dt = seconds(10)

% synchronize your table like below: 
synched_table = synchronize(TT1,TT2,'regular','nearest','TimeStep',dt);  % you can also use 'SampleRate',Fs. Fs must be in Hz(frequency)

[Inouss]

Thank you Lunu

[Luna]

Your welcome :)

Answer 2

[David Hill]

B=zeros(max(A(:,1)),1);
B(A(:,1))=A(:,2);

If you don't like all the zeros, then you could use a sparse matrix.

B=sparse(A(:,1),1,A(:,2));

[Inouss]

Thank you David, see above the examples of my csv files