How to make section distance of temperature

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

data=xlsread('ctd_data.xlsx');
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
shading interp
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 :

Answer 1

[jonas]

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.

data=xlsread('ctd_data.xlsx');
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
shading interp
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!

[Anom Sulardi]

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!