How do I compare data sets of different lengths?

We have a total of 4 columns of data 2 columns are for one program and the other 2 columns are for another program. We are trying to correlate the data and find the slope of the line between the all 4 columns of data. The issue is that the data sets are of unequal length because the frequency of data collection we are using on two pieces of equipment are different and cannot be changed. So, for example, one piece of equipment is taking data at a speed of 100 data points per second where the other piece of equipment is taking one data point per second. This causes the data sets to be completely different in length. I am compiling all 4 columns into one spreadsheet.

As of now, the first two columns start in A and B are begin at row 35 and end at 195. The other two columns are C and D and begin at row 35 and end at 4554. We are trying to plot the data on one line and compare the 4 columns of data onto one plot. A previous code was written and is provided below.

%%Axial Reducer Data Analysis
clc;
clear;
%Call all the data, has to be manually changed
count = xlsread('AR3 Formatted',1, 'A35:A195');
ForceLV = xlsread('AR3 Formatted',1, 'B35:B195');
count2 = xlsread('AR3 Formatted',1, 'C35:C4554');
ForceMM = xlsread('AR3 Formatted',1, 'D35:D4554');
%find the normal factor
num=ceil(size(count2)/size(count))
%setup the averaged array
blockSize= [num, 1];
meanFilterFunction = @(theBlockStructure) mean2(theBlockStructure.data(:));
% Now do the actual averaging (block average down to smaller size array).
ForceMM = blockproc(ForceMM, blockSize, meanFilterFunction);
%will still be a little off, just subtract the first few numbers till the
%length is the same. 
ForceLV=ForceLV(6:end);
plot(ForceLV, ForceMM);
%factor=Strainave\force
title('Axial Reducer Calibration')
xlabel('Force Read by Labview (N)')
ylabel('Force Read by MM (N)')

[Luna]

Why are you using blockproc? Is your data an image?

If you have a different lenghts of data due to your sampling time, create a time vector and make an interpolation.

Read about below function:

interp1

[Jonathan Copley]

This is the data that I have from the two different pieces of equipment. The code was written by a previous group to try and find the correlation. My group has been tasked by improving on their code.

I am unsure of how to use the interp 1 function with the the two columns per equipment. That is what is confusing me.

[Star Strider]

They are not simply of different lengths, they are of significantly different orders of magnitude. You need th re-scale one or the other (or both) to compatible scales to use interp1.

[Jonathan Copley]

How would you re-scale them to be compatible scales? Do you have any suggestions?

[Star Strider]

I have no idea.

I don’t know the units for either one. That makes any reliable scaling impossible.

[Jonathan Copley]

We are converting strain into Force. the first two columns are strain and the second two are in Newtons.

Answer 1

[Haritha]

Hi,

First apply padding to matrices for making all the columns as same size. Now it is possible to compare all the columns

[Jonathan Copley]

Would you recommend filling in the smaller columns with zeros on the end? In other words, I would fill in zeros for the rest of the values for the first two columns until they match the longer array. For the code, I am still trying to compare strain to Force, so the x-axis is still very small. When I try and compare the two, I am not seeing a line just

Answer 2

[Haritha]

yes

[madhan ravi]

@Haritha if you put up an answer use a single answer section don‘t post multiple answers in a single thread.