Why doesn’t contour plot run when I add ‘ShowText’? Is my data set too big?

7 vues (au cours des 30 derniers jours)
Kristine
Kristine le 24 Fév 2025
Commenté : Kristine le 27 Fév 2025

Hi y’all. I am trying to create an oceanographic t-s contour plot (salinity as x-axis, temperature as y-axis, and contour defined by density). When I run the code without ‘ShowText’, it takes a few seconds, but it runs. But MATLAB can’t produce a plot when I want to add labels on the contour lines. Is it because my data set it too long (6522 rows)? Is the function slowing everything down? My code is shown in comments below.

  2 commentaires
Kristine
Kristine le 24 Fév 2025
function [rho] = density(S,T)
RHO0 = R0+T.*(R1+T.*(R2+T.*(R3+T.*(R4+T.*R5))));
A = A0+T.*(A1+T.*(A2+T.*(A3+T.*A4)));
B = B0+T.*(B1+T.*B2);
RHO = RHO0+S.*(A+B.*sqrt(S)+C.*S);
rho = RHO ./ 1000;
end
figure(1)
T = stations.Temperature;
S = stations.Salinity;
[X,Y] = meshgrid(S,T);
Z = density(X,Y);
contour(X, Y, Z, 'color', 'k', 'ShowText','on', "LabelFormat","%0.1f");
Kristine
Kristine le 24 Fév 2025
I actually ended up leaving the code to run and it took maybe a half hour and produced this graph. I'm not sure how to prevent the repetition on the contour text. I'm not sure why it shows so many.

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dpb
dpb le 24 Fév 2025
Modifié(e) : dpb le 24 Fév 2025
We don't have the ranges for T,S but they appear to be pretty closely spaced from the plot. Either only plot every Nth point or use the 'LabelSpacing' named parameter to reduce the number of labels shown.
The idea with data reduction---
T = stations.Temperature;
S = stations.Salinity;
nSpacing=10;
[X,Y] = meshgrid(S(1:nSpacing:end),T(1:nSpacing:end));
Z = density(X,Y);
contour(X, Y, Z, 'color', 'k', 'ShowText','on', "LabelFormat","%0.1f");
Or, with all data plotted but reducing the number of labels shown...
T = stations.Temperature;
S = stations.Salinity;
nSpacing=10;
[X,Y] = meshgrid(S,T);
Z = density(X,Y);
contour(X, Y, Z, 'color', 'k', 'ShowText','on', "LabelFormat","%0.1f",'LabelSpacing',144*nSpacing);
The default for 'LabelSpacing' is 144 points, the above sets a multiplier on that value. This is a single vaue for the whole plot, given the appearance that the point density is higher at larger X, you may need to use a variable selection of point spacing instead to get a more uniform spread of written labels.
  5 commentaires
dpb
dpb le 25 Fév 2025
Modifié(e) : dpb le 25 Fév 2025
Or, alternatively, limit the number of points overall...
NT=50; % cut it down to 2500 points overall, work from there
NS=50;
T=stationALL.PotentialTemperatureITS90DegC; % get the original
S=stationALL.SalinityPracticalPSU;
T1=linspace(min(T),max(T),NT); % vectors within grid ranges
S1=linspace(min(S),max(S),NS);
[X,Y]= meshgrid(S1,T1); % subsequent grid
Z= density(X,Y);
contour(X,Y,Z,'color','k','ShowText','on');
Kristine
Kristine le 27 Fév 2025

This helped! Thank you!

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