How do I compare two data sets of unequal length?

63 views (last 30 days)
DH on 8 Aug 2018
Commented: Adam Danz on 14 Aug 2018
I have two sets of data, taken on different days, from the same sensor. The temperature was swept from 26C to -30C to 80C and back to 26C. The sensor was read periodically during the temperature sweep. The data sets consist of a temperature column, and another column representing the sensor readings. I would like to take a difference between the two sets of sensor readings, generating another data set having a column of temperatures, and a column of differences between the two original sets of sensor readings. If each data set had exactly the same vector of temperatures, I could just subtract one vector of sensor readings from the other. However, the temperature vectors do not contain exactly the same temperatures, and they don't even have the same number of elements. I would like to interpolate one set of temperatures and sensor readings to match the temperatures of the other, so I have two data sets of the same size, at the same temperatures. One complicating factor is that, due to sensor hysteresis with respect to temperature, the sensor readings are different on the downward temperature ramps from those on the upward temperature ramp. Therefore I can't sort the data on temperature, because that would mix the upward and downward ramps. If I could sort the data on temperature, I could use timeseries objects, with temperature in place of time. However, that won't work in this case.
DH on 9 Aug 2018
I think I see how to do it. Your mention of interp1 clued me in.
data1 = readtable([tstfldr 'dataset1.csv']);
data2 = readtable([tstfldr 'dataset2.csv']);
[uniquetemps, it, iu] = unique(data1.Temperature, 'stable');
data1reduced = data1(it,:);
interpSnsr1 = interp1(data1reduced.Temperature, ...
data1reduced.SensorData, data2.Temperature);
df = interpSnsr1 - data2.SensorData;
Thank you for your help.

Sign in to comment.

Accepted Answer

DH on 14 Aug 2018
Problem solved - see response from Adam Danz on 8 Aug 2018 at 20:10, and my response - DH on 9 Aug 2018 at 12:15.

More Answers (2)

Yuvaraj Venkataswamy
Yuvaraj Venkataswamy on 8 Aug 2018

Sign in to comment.

Yuvaraj Venkataswamy
Yuvaraj Venkataswamy on 8 Aug 2018
if true
id = ismember(dataset1', dataset2', 'rows');
X = 1:size(dataset1, 2);
Y = X(id);
  1 Comment
Adam Danz
Adam Danz on 8 Aug 2018
This method won't work on your current data, either.

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by