How to make a colormap inside an area created from points

Hello,

I have excel file with 3 columns: Distance, Depth and Temperature (Please see the attached file). The question is how to make a colormap only in the area (from the surface to the river bed). See the picture below, this is what I want to create

Here is my code. My problem: the colormap is outside the depth, even I used the boundary function. Please see the picture below

data=xlsread('Day1_1704.xlsx');
x=data(:,1); %first colum in excel file, as distance
y=data(:,2);%second colum in excel file, as depth
c=data(:,3); %c is the concentration of  Temperature, third column
%[X,Y] = meshgrid(x,y);
%f = scatteredInterpolant(x,y,c);
%Z = f(X,Y);
%mesh(X,Y,Z) %interpolated

subplot(2,1,1) 
scatter(x,y,30,c,'filled')
colorbar
%xlim([0 18])
%ylim([-20 0])
axis tight; hold on
shading interp
ylabel('Depth (m)'); 
title('Temperature distribution');
view(2)
colorbar
%caxis([30 32]) %If the scale is too large, values not shown well, change scale

subplot(2,1,2)  
[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); %assign c values to x y
vg = f(xg,yg);% assign c values to finer pixel xg yg

b=boundary(x,y,1); %create the boundary of depth in each cross section
inmask = inpolygon(xg(:),yg(:), x(b),y(b));%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
colorbar
xlabel('Distance (km)'); 
ylabel('Depth (m)');

The upper graph is the dots from raw data, the last dot in each distance is the river bed. The second graph is the colormap that I created. Could you please help me to create the colormap only from the surface to the riverbed

[Adam]

The problem is with the geometry you are creating rather than the colourmap isn't it? The colourmap will just apply itself to whatever geometry you give it.

I would assume you need to create a surface/patch with those low points for each column as vertices, then they would be joined together rather than just ending up with a simple containing shape like you currently have. It isn't my area of expertise though.

[jonas]

There seems to be something wrong with your boundary function, as you can see if you type plot(x(b),y(b))

[Truong Nguyen]

Thanks Adam and Jonas. Yes, there is problem with the boundary function.

@Adam: You mean that I should create another map (e.g. in Black) for the lower part and overlay with the current one?

I used plot(x(b),y(b)). So the boundary function did not consider all the points at each distance. Do you have any idea to connect these points @Jonas?

[Adam]

I mean the colourmap is fine, it is the geometry that you plot that needs fixing.

[jonas]

change the boundary function to this

for i=1:numel(unique(x))
    [~,a(i)]=min(y(x==i))
end
b=[444-15 1 cumsum(a)];

It's not the most elegant solution but it works. I don't know why the default function is not working.

[Truong Nguyen]

Thanks Jonas. Your function is quite good. I also solved this problem. Just make the boundary by taking the last point at each distance. This is not so good, but it still works.

for i=1:(length(x)-1)% 1 to end of the distance
    if x(i+1)~=x(i)
        j=j+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;

Thanks so much for all your help

[jonas]

Nice! Happy to help.

[Anom Sulardi]

When I apply to my data using the boundary above, why is not working? they said "Array indices must be positive integers or logical values."

[jonas]

Need to see your data, code and desired result in order to help you. Better yet, post a new question!

[Anom Sulardi]

hi Jonas,

I have make the new question ones, would you please to stop by then? Thank you

https://www.mathworks.com/matlabcentral/answers/493408-how-to-make-section-distance-of-temperature