Aligning then subtracting unequal length column vectors

Hello, i have 2 vectors xspots and xgrid

xspots = [
2600.00
2679.00
2802.00
2924.00
3046.00
3169.00
3291.00
3413.00
3536.00
3658.00
3781.00];

xgrid = [
2680.00
2803.00
2926.00
3049.00
3172.00
3294.00
3417.00
3539.00];

Crucially they are not the ame length

what I want to do is locate in both, the nearest value to a reference (called ref) i.e. ref=3200.

I then want to align these two vectors such that the values closest to ref lign up (i.e. this will then be the values 3169 & 3172.)

Then I want the diff between xspots and xgrid in this aligned state.

This was my attempt, but its in 2 parts.

           ref=3200;
           mask = xgrid(:,1) < ref;              
           xgrid(mask,:) = [];
           
           mask = xspots(:,1) < ref;
           xspots(mask,:) = [];
           
           n=min(numel(xspots,xgrid));
           data=[];
           for i=1:n
                 data(i,1)=xspots(i);
                 data(i,2)=xgrid(i);                 
           end    
           data(:,3)=data(:,1)-data(:,2)
           %% and then repeat this for > ref.... but it seems long winded.
           
           
               
               
       

[Dyuman Joshi]

(From what I understood) Define a function so that you can call it for different inputs -

function data = fun(xgrid, xspots, ref)
    mask1 = xgrid < ref;              
    xgrid(mask1,:) = [];
           
    mask2 = xspots < ref;
    xspots(mask2,:) = [];
           
    n = min(numel(xspots,xgrid));
    data = [xspots(1:n) xgrid(1:n)];
    data(:,3) = dist(:,1)-dist(:,2);
end

[Jason]

Thanks. But this only considers <ref so throws away nearly hakf the data. I need all the data that is overlapped.

[Dyuman Joshi]

Could you please specify what is the expected output by using the data attached (if possible, with step by step calculation)?

[Jason]

This is the output I need. Notice how I align the two vectors at the ref. value, and then where there is overlap perform the subtraction

[Jason]

I forgot to say, i need the 1st column values together with tge 3rd column (as i will be plotting these)

Answer 1

[Voss]

xspots = [
2600.00
2679.00
2802.00
2924.00
3046.00
3169.00
3291.00
3413.00
3536.00
3658.00
3781.00];

xgrid = [
2680.00
2803.00
2926.00
3049.00
3172.00
3294.00
3417.00
3539.00];

ref=3200;

[~,idx1] = min(abs(xspots-ref));
[~,idx2] = min(abs(xgrid-ref));
n1 = numel(xspots);
n2 = numel(xgrid);
ii = intersect((1:n1)-idx1,(1:n2)-idx2);

difference = xspots(idx1+ii)-xgrid(idx2+ii)

difference = 8x1

-1 -1 -2 -3 -3 -3 -4 -3

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result = [xspots(idx1+ii) difference]

result = 8x2

2679 -1 2802 -1 2924 -2 3046 -3 3169 -3 3291 -3 3413 -4 3536 -3

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[Jason]

thankyou thats perfect!

[Voss]

You're welcome!