MATLAB: How would you make a contour plot of a 3 column matrix

contourMATLABplotscatter

Hello,
I am currently trying to make a contour plot of distance-depth with pCO2 as the z value (in the excel file there are multiple columns but i only need those three). This takes the form of three columns of equal size, however I looked in the forums and it is apparently not possible. Data from the third column needs to be associated to the others in some way that allows the contour plot. My question is: if not possible, how then would you represent a profile such as this, with distance on x, depth on y and z as the value studied ?? I have thought about a scatter but I can't figure out the parameters to trace for example lines of equal values to make it look better than just scattered points… Any ideas ?? Thank you !!

Best Answer

Hi Louis van Herwijnen
this is John BG <mailto:jgb2012@sky.com jgb2012@sky.com>
1.-
acquiring data from the provided Excel file
clear all;clc;close all
A=xlsread('AR07W_2011processed.xls')
L=A(:,1)                         % reading distances
taking only 2 decimals
N=2
L=1/10^N*floor(L*10^N)
.
checking whether grid is uniform
.
[D,ni,na]=unique(L);             
ni(1)=1   % correction for 1st row because spreadsheet 1st row contains var names only, not numerical data
nD=[diff(ni); numel(L)-ni(end)+1]  % amount of measurements at different depths, on same distance
.
The coordinates to use are D: Distance W: Depth
.
d=A(:,1);
w=A(:,2);
% max min values of coordinates:
min(d)
% =

%      0
max(d)
%  =

%      6.887000000000001e+02
min(w)
%  =
%    1.400000000000000
max(w)
% =
%      3.675300000000000e+03
.
ok, now we see it's a non-uniform grid
2.-
 acquiring measurements
T         =  A(:,3);      % Temperature Celcsius
S         =  A(:,4);      % Salinity [psu]
TA        =  A(:,4);      % TA umol/kgSW
TCO2      =  A(:,5);      % TCO2 umol/kgSW
TpCO2     =  A(:,6);      % pCO2 uatm
pH        =  A(:,7);      % pH
O2        =  A(:,8);      % O2 [umol/kgSW
3.-
Example plot without interpolation, on same distance
k=3
hf(1)=figure(1);plot(w([ni(k):1:ni(k+1)-1])',T([ni(k):1:ni(k+1)-1])')
xlabel('W:depth');ylabel('T(ºC)')
title(['Temperature measurements at distance d = ' num2str(d(ni(k)))]);
grid on
% 000-1
.
non-uniform grid of 2D reference points
.
hf(2)=figure(2);plot(d,w,'ro');grid on;grid minor
xlabel('D:distance');ylabel('W:depth')
% 000-2
.
Temperature interpolation
.
F_Temperature=scatteredInterpolant(d,w,T)
% F=scatteredInterpolant(A(:,1),A(:,2),A(:,3))
Q=4  % interpolation factor 
d_uniform_range=linspace(min(d),max(d),Q*numel(nD)-1)
w_uniform_range=linspace(min(w),max(w),Q*numel(nD)-1)
[D,W]=meshgrid(d_uniform_range,w_uniform_range)
T2=F_Temperature(D,W)
hf(3)=figure(3);surf(D,W,T2)
campos([4401.80925645085   23683.44745915113   25.18900384688])
xlabel('D:distance');ylabel('W:depth')
title(['Temperature - interpolation factor Q = ' num2str(Q)])
% 001
.
4.- Temperature contours
.
hf(4)=figure(4);hT_surfc=surfc(D,W,T2)
campos([5578.878486985600   7013.723961265031   21.490607228584])
xlabel('D:distance');ylabel('W:depth')
title('Temp contour projections')
% 002
.
The projected contours are available in here:
 hT_surfc(2)
 ans = 
   Contour with properties:
     LineColor: 'flat'
     LineStyle: '-'
     LineWidth: 0.500000000000000
          Fill: 'off'
     LevelList: [1×9 double]
         XData: [71×71 double]
         YData: [71×71 double]
         ZData: [71×71 double]
.
You can carry on working on the contour lines by acquiring the 2D curves in the following way:
x_T_contours=hT_surfc(2).XData
y_T_contours=hT_surfc(2).YData
z_T_contours=hT_surfc(2).ZData
hf(5)=figure(5);contourf(T2,10)
xlabel('D:distance');ylabel('W:depth')
title('Temperature contours with contourf')
% 003
.
Once a surface is available it may be particularly useful to 1: zoom in and out and 2: check data with the cursor, that I prefer call it marker:
.
5.-
Salinity [psu] Surface
.
F_Salinity=scatteredInterpolant(d,w,S)
S2=F_Salinity(D,W)
hf(6)=figure(6);surf(D,W,S2)
campos([4401.80925645085   23683.44745915113   25.18900384688])
xlabel('D:distance');ylabel('W:depth')
title(['Salinity - interpolation factor Q = ' num2str(Q)])
hf(7)=figure(7);hS_surfc=surfc(D,W,S2)
campos([5578.878486985600   7013.723961265031   21.490607228584])
xlabel('D:distance');ylabel('W:depth')
title('Salinity contour projections')
% 004
x_S_contours=hS_surfc(2).XData;
y_S_contours=hS_surfc(2).YData;
z_S_contours=hS_surfc(2).ZData;
hf(8)=figure(8);contourf(T2,10)   
xlabel('D:distance');ylabel('W:depth')
title('Temperature contours with contourf')
6.-
TA [umol/kgSW] surface
F_TA=scatteredInterpolant(d,w,TA)
TA2=F_TA(D,W)
hf(9)=figure(9);surf(D,W,TA2)
campos([4401.80925645085   23683.44745915113   25.18900384688])
xlabel('D:distance');ylabel('W:depth')
title(['TA - interpolation factor Q = ' num2str(Q)])
hf(10)=figure(10);hTA_surfc=surfc(D,W,S2)
campos([5578.878486985600   7013.723961265031   21.490607228584])
xlabel('D:distance');ylabel('W:depth')
title('TA contour projections')
% 005
x_TA_contours=hTA_surfc(2).XData
y_TA_contours=hTA_surfc(2).YData
z_TA_contours=hTA_surfc(2).ZData
hf(11)=figure(11);contourf(TA2,10)   
xlabel('D:distance');ylabel('W:depth')
title('TA contours with contourf')
7.- TCO2 [umol/kgSW] surface
F_TCO2=scatteredInterpolant(d,w,TCO2)
TCO22=F_TCO2(D,W)
hf(12)=figure(12);surf(D,W,TCO22)
campos([4401.80925645085   23683.44745915113   25.18900384688])
xlabel('D:distance');ylabel('W:depth')
title(['TCO2 - interpolation factor Q = ' num2str(Q)])
hf(13)=figure(13);hTCO2_surfc=surfc(D,W,TCO22)
campos(   1.0e+04 *[  -0.486868459634731   1.534198637901339   0.281087905547732])
xlabel('D:distance');ylabel('W:depth')
title('TCO2 contour projections')
% 006



x_TCO2_contours=hTCO2_surfc(2).XData
y_TCO2_contours=hTCO2_surfc(2).YData
z_TCO2_contours=hTCO2_surfc(2).ZData
hf(14)=figure(14);contourf(TCO22,10)   
xlabel('D:distance');ylabel('W:depth')
title('TCO2 contours with contourf')
8.- pCO2 [uatm] surface
F_TpCO2=scatteredInterpolant(d,w,TpCO2)
TpCO22=F_TpCO2(D,W)
hf(15)=figure(15);surf(D,W,TpCO22)
campos([4401.80925645085   23683.44745915113   25.18900384688])
xlabel('D:distance');ylabel('W:depth')
title(['TpCO2 - interpolation factor Q = ' num2str(Q)])
hf(16)=figure(16);hTpCO2_surfc=surfc(D,W,TpCO22)
campos(   1.0e+04 *[  -0.486868459634731   1.534198637901339   0.281087905547732])
xlabel('D:distance');ylabel('W:depth')
title('TpCO2 contour projections')
% 006
x_pCO2_contours=hTpCO2_surfc(2).XData
y_pCO2_contours=hTpCO2_surfc(2).YData
z_pCO2_contours=hTpCO2_surfc(2).ZData
hf(17)=figure(17);contourf(TpCO22,10)   
xlabel('D:distance');ylabel('W:depth')
title('TpCO2 contours with contourf')
9.- Acidity [pH] surface
F_pH=scatteredInterpolant(d,w,pH)
pH2=F_pH(D,W)
hf(18)=figure(15);surf(D,W,pH2)
campos([4401.80925645085   23683.44745915113   25.18900384688])
xlabel('D:distance');ylabel('W:depth')
title(['pH - interpolation factor Q = ' num2str(Q)])
hf(19)=figure(16);hpH_surfc=surfc(D,W,pH2)
campos(   1.0e+04 *[  -0.486868459634731   1.534198637901339   0.281087905547732])
xlabel('D:distance');ylabel('W:depth')
title('pH contour projections')
% 006
x_pH2_contours=hpH_surfc(2).XData
y_pH2_contours=hpH_surfc(2).YData
z_pH2_contours=hpH_surfc(2).ZData
hf(20)=figure(17);contourf(pH2,10)   
xlabel('D:distance');ylabel('W:depth')
title('pH contours with contourf')
10.- Oxygen O2: [umol/kgSW] surface
F_O2=scatteredInterpolant(d,w,O2)
O22=F_O2(D,W)
hf(21)=figure(15);surf(D,W,O22)
campos([4401.80925645085   23683.44745915113   25.18900384688])
xlabel('D:distance');ylabel('W:depth')
title(['O2 - interpolation factor Q = ' num2str(Q)])
hf(22)=figure(16);hO2_surfc=surfc(D,W,O22)
campos(    1.0e+04 *[-0.461106553630150   1.377458945573147   0.001065817992402])
xlabel('D:distance');ylabel('W:depth')
title('O2 contour projections')
% 006
x_O22_contours=hO2_surfc(2).XData
y_O22_contours=hO2_surfc(2).YData
z_O22_contours=hO2_surfc(2).ZData
hf(23)=figure(17);contourf(O22,10)   
xlabel('D:distance');ylabel('W:depth')
title('O2 contours with contourf')
.
saving results
.
save('Excel_TSal_et_al_variables.mat')    % load with : load(''Excel_TSal_et_al_variables.mat'')
savefig(hf,'AllFigures.fig')                       % load with : openfig('AllFigures.fig')
Louis
if you find this answer useful would you please be so kind to consider marking my answer as Accepted Answer?
To any other reader, if you find this answer useful please consider clicking on the thumbs-up vote link
thanks in advance for time and attention
John BG
<mailto:jgb2012@sky.com jgb2012@sky.com>
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