Filtering column 2 and keeping column 1

I'm having an issue with filtering out data from column 2 that is below a certain desired output, but still keeping the time from column 1 to plot. I am fairly new to MatLab and it won't get rid of the negative outputs either.

This is my current code.

fs = 15;

rawData = xlsread('Total 4 Foot Lamp Lifecycle Testing.xlsx');

filteredData = lowpass(rawData(:,2),8,fs);

Any help is appriciated. Thank you.

Answer 1

[Walter Roberson]

mask = filteredData >= THRESHHOLD;

selected_time = rawData(mask,1);
selected_filtered_data = filteredData(mask);

However, if you proceed to

plot(selected_time, selected_filtered_data)

then plot() is going to draw right across the gaps. If your purpose is to plot and you want gaps in the plot, then you are better off using

mask = filteredData < THRESHHOLD;
filteredData(mask) = nan;
time = rawData(:,1);
plot(time, filteredData);

This inserts NaN in place of data that is below the threshold. When you go to plot() then plot() knows to leave gaps at all non-finite values (so gaps at NaN, at -inf, and at +inf)