How do I find angle of deviation between a set of points and the bounds of a polygon?

I have a few data being read from an excel sheet. This data is being passed into a function which checks if the data is within the bounds of a polygon (made from the function inpolygon using corner points), and is being plotted on a map. How do I find the angle of deviation between these points and the polygon bounds?

Is it possible for me to fit a line into the data points and check? I have attached an output plot for refrence

Code for reading the data and passing it into the function-

T = readtable('plot1.xlsx',)
checkingcode(T)

Code for checking the data if it is in bound or no-

%defining route bounds---------------
ats = readtable('ATS.xlsx');  
lat10=[ats.lat1(1),ats.lat2(1)];
lon10=[ats.lon1(1),ats.lon2(1)];

[x10, y10]= mfwdtran(mstruct,lat10,lon10);

X = [x10,fliplr(x10)];
Y = [y10,fliplr(y10)-d];
%defining route bounds---------------

%checking if data is within the bound--------
[journeys.x, journeys.y] = mfwdtran(mstruct, journeys.latitude, journeys.longitude);  %transform the flights latitude and longitude
in = inpolygon(journeys.x, journeys.y, X, Y);
[groupid, flights] = findgroups(journeys.flight);%assign unique id to each flight and apply to rows of the table
inratio = splitapply(@(in)nnz(in)/numel(in), in, groupid);  %ratio of points in polygon to points in flight
selectedflights = flights(inratio >= 0.9);  %for flights that have 70% of their journey in the polygon
selectedjourneys = journeys(ismember(journeys.flight, selectedflights), :);  %portion of the table with only the selected flights.
%checking if data is within the bound--------
%plotting------
plot(x10,y10,'-','color','m');%plotting ats bound 1
hold on;
plot(x10,y10-d,'-','color','m'); %plotting parallel bound of ats bound 1
[sx, sy] = mfwdtran(mstruct, selectedjourneys.latitude, selectedjourneys.longitude);
scatter(sx,sy,[],color, 'Marker','+') %plotting all flights in between the ats route
%plotting------

[harman bhaveja]

Really need this... Could someone please help? ://