# How to make section distance of temperature

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Anom Sulardi on 27 Nov 2019
Commented: Anom Sulardi on 27 Nov 2019
I would like to make section distance from depth, section distance, and temperature data with bottom topography shown (as the picture shown). Here is my excel data, and I have tried to programing on syntax as follow. But it's not working especially for the boundary loop. Is there any idea for this? I utilize Matlab 2019a
clc
clear
x=data(:,5); %first colum in excel file, as distance
y=data(:,3)*-1;%second colum in excel file, as depth
c=data(:,4); %c is the concentration of Temperature
figure(1)
scatter(x,y,30,c,'filled')
colorbar
axis tight; hold on
ylabel('Depth (m)');
title('Temperature distribution');
figure(2)
[xg,yg] = meshgrid(min(x):0.1:max(x),min(y):0.1:max(y)); %make a grid to contain x,y
f = scatteredInterpolant(x,y,c,'linear'); %assign c values to x y
vg = f(xg,yg);% assign c values to finer pixel xg yg
for i=1:(length(x)-1)% 1 to end of the distance
if x(i+1)~=x(i)
j=i+1;
bx(j)=x(i);
by(j)=y(i);
end
end
bx(j+1)=x(length(x));
by(j+1)=y(length(y));
bx(j+2)=x(length(x));
by(j+2)=0;
b=boundary(x,y,1);
inmask = inpolygon(xg(:),yg(:), bx , by );%define which pixel exist in the polygon
vg(~inmask) = nan; %NAN values for the pixel not in the polygon
h = pcolor(xg,yg,vg); %ploting in 2D of vg by color
h.EdgeColor = 'none'; %to get rid off the edge line
h.FaceColor = 'interp';
colorbar
xlabel('Distance (km)');
ylabel('Depth (m)');
Desired picture :
result syntax :

jonas on 27 Nov 2019
Edited: jonas on 27 Nov 2019
Simply skipping the loop and changing the line
inmask = inpolygon(xg(:),yg(:), bx , by );%define which pixel exist in the polygon
to
inmask = inpolygon(xg(:),yg(:), x(b) , y(b) );%define which pixel exist in the polygon
Gives more or less the desired result. The boundary() function does not seem to capture all the corners though.
Here is a better method which works because you are working with grouped data, i.e. several measurements on the exact same depth.
x=data(:,5); %first colum in excel file, as distance
y=data(:,3)*-1;%second colum in excel file, as depth
c=data(:,4); %c is the concentration of Temperature
figure(1)
scatter(x,y,30,c,'filled')
colorbar
axis tight; hold on
ylabel('Depth (m)');
title('Temperature distribution');
figure(2)
[xg,yg] = meshgrid(min(x):0.1:max(x),min(y):0.1:max(y)); %make a grid to contain x,y
f = scatteredInterpolant(x,y,c,'linear'); %assign c values to x y
vg = f(xg,yg);% assign c values to finer pixel xg yg
%find boundary
[g,xd] = findgroups(x)
yd_top = splitapply(@min,y,g)
yd_bot = splitapply(@max,y,g)
yd = [yd_top;flip(yd_bot)];
xd = [xd;flip(xd)]
inmask = inpolygon(xg(:),yg(:), xd , yd );%define which pixel exist in the polygon
vg(~inmask) = nan; %NAN values for the pixel not in the polygon
h = pcolor(xg,yg,vg); %ploting in 2D of vg by color
h.EdgeColor = 'none'; %to get rid off the edge line
h.FaceColor = 'interp';
colorbar
xlabel('Distance (km)');
ylabel('Depth (m)');
cheers!

#### 1 Comment

Anom Sulardi on 27 Nov 2019
Thank you in advance for your great work, it's really working well. I would like to appreciate on your time and work. Have a nice day!