# Extracting a particular data from the original data

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sam moor on 14 Nov 2016
Edited: Star Strider on 14 Nov 2016
I have a data file named rd.txt attached below. 1st column data refers to time and all other columns refers the corresponding distance. Now I want to extract the data for 0.02,0.04,0.06,...60.00 sec (at a difference of 0.02) from 1st column and corresponding distances. Is there a way to extract data from the original data for a particular values? Your answer is highly appreciated. Thank you.

Star Strider on 14 Nov 2016
This works for me without error:
fidi = fopen('sam moor rd.txt','rt');
Dcell = textscan(fidi, repmat('%f',1,9), 'CollectOutput',1, 'Delimiter',' ');
D = cell2mat(Dcell);
L = size(D,1);
t = D(:,1);
q = length(t > 0)/L;
ti = 0 : 0.02 : max(t); % Interpolation Vector
Di = interp1(t, D(:,2:end), ti, 'linear'); % Interpolated Data
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Star Strider on 14 Nov 2016
I eliminated the first column from the ‘Di’ matrix, because that is the time vector to use for the interpolation.
Adding the ‘rd_new’ assignment will give you the complete, interpolated ‘rd’ matrix:
fidi = fopen('sam moor rd.txt','rt');
Dcell = textscan(fidi, repmat('%f',1,9), 'CollectOutput',1, 'Delimiter',' ');
D = cell2mat(Dcell);
L = size(D,1);
t = D(:,1);
ti = 0.02 : 0.02 : max(t); % Interpolation Vector
Di = interp1(t, D(:,2:end), ti, 'linear'); % Interpolated Data
rd_new = [ti' Di]; % Complete Interpolated ‘rd’ Matrix
EDIT Corrected to begin ‘ti’ at 0.02 rather than 0.00.

Image Analyst on 14 Nov 2016
I suggest you read the the FAQ on comparing floating point numbers and then use that or try a new function called ismembertol() to find out which rows match your desired times. One might think intersect() might work but because of the FAQ I referred you to, I have my doubts.

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