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## Save variable from each run through of a loop into .mat file?

Asked by BOB

### BOB (view profile)

on 14 Sep 2018
Latest activity Answered by KSSV

### KSSV (view profile)

on 14 Sep 2018
Accepted Answer by KSSV

### KSSV (view profile)

Hi folks,
I have my looped function
if true
for Z = 1:length(ev_longitude)
x1 = -4:10; %Grid x-range
A = min(ev_longitude(Z),st_longitude(Z)); %Determine min x coordinate of line
B = max(ev_longitude(Z),st_longitude(Z)); %Determine max x coordiante of line
x = [A B]; %x-range of line
y1 = 56:63; %Grid y-range
C = min(ev_latitude(Z),st_latitude(Z)); %Determine min y coordinate of line
D = max(ev_latitude(Z),st_latitude(Z)); %Determine max y coordinate of line
y = [C D]; %y-range of line
lxmb = @(x,mb) mb(1).*x + mb(2); %Line equation: y = m*x+b
coefficients = polyfit([A, B], [C, D], 1); %Determine line coefficients
m = coefficients (1); %Gradient
b = coefficients (2); %y-value intercept
mb = [m b]; %Matrix of [slope intercept] values
L1 = lxmb(x,mb); %Calculate Line #1 = y(x,m,b)
start_of_line = [A C]; %Start of line
end_of_line = [B D]; %End of line
hix = @(y,mb) [(y1-mb(2))./mb(1); y1]; %Calculate horizontal intercepts
vix = @(x,mb) [x1; lxmb(x1,mb)]; %Calculate vertical intercepts
hrz = hix(x(1:end),mb)'; %[X Y] Matrix of horizontal intercepts
vrt = vix(y(1:end),mb)'; %[X Y] Matrix of vertical intercepts
hvix = [start_of_line; hrz; vrt; end_of_line]; %Concatanated ‘hrz’ and ‘vrt’ arrays
srtd = unique(hvix,'rows'); %Remove repeats and sort ascending by ‘x’
Longitude_Values = srtd(:,1);
Latitude_Values = srtd(:,2);
i = find((Latitude_Values<=D) & (Latitude_Values>=C)); %Remove values beyond the drawn line
Final_Latitude_Values=Latitude_Values(i); %Remove values beyond the drawn line
ii = find((Longitude_Values<=B) & (Longitude_Values>=A)); %Remove values beyond the drawn line
Final_Longitude_Values=Longitude_Values(i); %Remove values beyond the drawn line
for j = 1:length(Final_Latitude_Values)-1 %Determine the distance per each segment
Segment_Distances(j) = sqrt((Final_Longitude_Values(j+1)-Final_Longitude_Values(j))^2 + (Final_Latitude_Values(j+1)-Final_Latitude_Values(j))^2); %euclidean distance in degrees.
end
Final_Segment_Distance_Per_Travel_Path = Segment_Distances(1:end) %Final segment per travel path
save('End_Data','Final_Segment_Distance_Per_Travel_Path')
clearvars -except ev_latitude ev_longitude st_latitude st_longitude
end
end
It produces a variable called Final_Segment_Distance_Per_Travel_Path. I want to save this value each time to a .mat file using the save function, without the previous value being overwritten each time the loop runs.
Thanks for any help.

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## 1 Answer

Answer by KSSV

### KSSV (view profile)

on 14 Sep 2018
Accepted Answer

Check this demo code:
n = 10 ; % loop count
filename='test.mat';
File = matfile(filename, 'Writable', true);
for i = 1:n
SE = rand(1,2) ;
DE = rand(1,3) ;
% save variables to file
File.SE(i,1:2) = SE ;
File.DE(i,1:3) = DE ;
end
clear File;

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