Plot a time-depth temperature contour graph

Hi guys,

This is my first time using Matlab ever, so as you can imagine I am a bit lost.

I have to plot a contour graph with time as x, depth as y and temperatures as z. The data looks like this on excel :

I looked for tutorials on Internet but I am completely lost. Could someone please give me some hints as to where to start, for example only how to make the data useable on Matlab ? I tried the 'xlsread' command but I have no idea what to do next... any king of help would be great ! Thank you !

[Merged from essentially same question]

Hi guys,

So I have this data and I am trying to plot a contour graph with : depth as Y, the hours as X, and the temperature as the data assigned to each depth and hour. But whatever I try, I have something that does not work, be it matrix dimension or something else. I do not understand how I should define each variable, X Y Z, when it shouldn't be too complicated ! does anyone have any kind of hints or help ? The blanks are simply times when the temperature could not be recorded, but that shouldn't be a problem in a contour plot should it ?? I am getting really desperate

Data file is https://www.mathworks.com/matlabcentral/answers/uploaded_files/95195/Plots.xls

[Walter Roberson]

What should happen for the places that are blank? Are those to be interpolated, or are they to be understood as outside of the image?

[Louis van Herwijnen]

No these are blank because the tide was rising : measurements could not always be carried out at those depths, so there is just no data at some times ! (which is also part of why I'm having trouble)

[Louis van Herwijnen]

So depth is the first line, time is the first column and everything else are temperature readings

Answer 1

[Walter Roberson]

data = xlsread('Plots.xls');
time_in_days = data(1,2:end);
depth = data(2:end,1);
temperature = data(2:end,2:end);
contourf(time_in_days, depth, temperature)
datetick('x', 'HH:MM')

[Louis van Herwijnen]

Mr Roberson, you saved my life !! thank you !!!

Answer 2

[Ruben]

Hi @Walter Roberson or anyone else who could help. I have a very similar problem. My imported data looks like this:

Is the Var1 column a datetime? I use the code below and get this error:

"Error using contourf

Input arguments must be numeric or objects which can be converted to double."

I've tried turning the datetime into a number with datenum (commented out below) but I haven't had success with that either. It gives the error:

"Error using datenum

DATENUM failed.

Caused by:

Error using datevec

The input to DATEVEC was not an array of character vectors or strings."

%% Import Data
filename = "Plots_mmddyyyy.dat";
A = readtable(filename);
Aopts = detectImportOptions(filename);

%% Partition Table Data Into Variables
Depth = A(1,2:end);
Time = A(2:end,1);
Temperature = A(2:end,2:end);

%Ttime = datenum(Time);

%% Plot
contourf(Time,Depth,Temperature)

[Walter Roberson]

Which MATLAB version are you using?

[Ruben]

R2022a.

Sorry for posting my question here as an answer in someone else's thread. I only read your recommendation after posting this. I read through the link you sent me and I have a better idea of how to ask questions in the future. Thanks for your patience.

[Walter Roberson]

%% Import Data
filename = "Plots_mmddyyyy.dat";
Aopts = detectImportOptions(filename);
A = readtable(filename, Aopts);

%% Partition Table Data Into Variables
Depth = A(1,2:end);
Time = A(2:end,1);
Temperature = A(2:end,2:end);

%Ttime = datenum(Time);

%% Plot
contourf(datenum(Time), Depth, Temperature)

[Ruben]

[Ruben]

I got an error message again. Same error message as before. Do you have any other suggestions? Thank you for your time!

[Walter Roberson]

%% Import Data
filename = "Plots_mmddyyyy.dat";
Aopts = detectImportOptions(filename);
A = readtable(filename, Aopts);

%% Partition Table Data Into Variables
Depth = A{1,2:end};
Time = A{2:end,1};
Temperature = A{2:end,2:end};

%% Plot
contourf(datenum(Time), Depth, Temperature)