Matching array dimensions when importing csv

Hi I'm trying to match the dimensions of two arrays so i can plot them. One is longer than the other, so I am trying to interpolate the data to create two equal arrays. My code is as follows:

close all;

measurementfile = 'FILE1_20.csv';
backgroundfile = 'FILE1_4.csv';

% Workings

% Load both files in

filelines1 = strtrim(strsplit(fileread(measurementfile), newline()));
startstop1 = find(ismember(upper(filelines1), {'BEGIN','END'})) - [0,2];

unit1 = filelines1(16);

T1 = csvread(measurementfile, startstop1(1), 0, [startstop1(1) 0 startstop1(2) 4]);

[~,filename1,ext1] = fileparts(measurementfile);

filelines2 = strtrim(strsplit(fileread(backgroundfile), newline()));
startstop2 = find(ismember(upper(filelines2), {'BEGIN','END'})) - [0,2];

unit2 = filelines2(16);

T2 = csvread(backgroundfile, startstop2(1), 0, [startstop2(1) 0 startstop2(2) 4]);

[~,filename2,ext2] = fileparts(backgroundfile);

% Determine unit and put into variables. Create y axis label.

if contains(unit1, "! DATA UNIT dB?V" )

    
    freq1 = T1(:,1);
    measured = T1(:,2);
    
    %%%%%%%%%
    xnew = linspace(min(freq1), max(freq1), 601);
    T1new = interp1(freq1, measured, xnew);

    %%%%%%%%%
    
    freq1new = T1new(:,1);
    measurednew = T1new(:,2);
    
    %%%%%%%%%%
    T1new = reshape(T1new, 601,1);
    T1new = [freq1new, T1new];
    %%%%%%%%%%
    
    freq2 = T2(:,1);
    background = T2(:,2);
    
    ylabelplot = "Power (dB\muV)";
   
end

Now T1new has the correct number of points, but doesn't come with the 4 additional columns of T2 (601x1 and 601x5 respectively). Is there a way to add the frequency column to T1new to verify the interpolation is correct - and to add the additional columns of zeros, as in T2? I've attached two example files for reference.