How to set scale range for a contour?

Hello,

I am trying to plot a contour from excel data with two colums. Is their any way to set the scale of both the axis in the data range and with label? I am attaching the contour plot i have obtained, I didnt understand why the x axis is from 1:2. Can some one please help me. Thanks in advance.

My code:

data = readtable('Abb73at42.xlsx');
dataArray = table2array(data);
contourf(dataArray);

Answer 1

[Star Strider]

The x-axis goes from 1 to 2 because the contour plot is of a (117x2) matrix. That also explains the range of the y-axis.

data = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/736719/Abb73at42.xlsx')

data = 117×2 table
       X         Y   
    _______    ______

    -69.793    1.3879
    -69.635    2.4547
    -69.537    3.4459
    -69.432     4.904
    -69.352    6.4546
    -69.334    7.5779
    -69.161    9.0059
    -68.937    10.381
    -68.975    11.324
    -68.975     12.41
    -68.975    13.496
    -68.889    14.557
    -68.548    16.102
    -68.435    17.943
    -68.376    19.148
    -68.172    20.606

figure
plot(data.X, data.Y)
grid
xlabel('X')
ylabel('Y')

More importantly, what information do you want to get from a contour plot of these data? That could provide an approach to getting a useful result.

.

[Vishnuvardhan Naidu Tanga]

Hello,

Thank you fro the quick response. I wanted to check the profile from the data. Is it possible to plot it as a contour as like in the figure i have uploaded with the data scale range instead of cell numbers?

With regards

[Walter Roberson]

No. Your desired contour requires 3 variables: X and Y independent plus one dependent variable. It is not possible to get the desired output from only that data.

You are getting cell numbers because you are only passing a single array to contour() and when you only pass a single array then it assumes that the x coordinates is 1 : number_of_columns and that the y coordinates are 1 : number_of_rows

[Star Strider]

It is.

data = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/736719/Abb73at42.xlsx')

data = 117×2 table
       X         Y   
    _______    ______

    -69.793    1.3879
    -69.635    2.4547
    -69.537    3.4459
    -69.432     4.904
    -69.352    6.4546
    -69.334    7.5779
    -69.161    9.0059
    -68.937    10.381
    -68.975    11.324
    -68.975     12.41
    -68.975    13.496
    -68.889    14.557
    -68.548    16.102
    -68.435    17.943
    -68.376    19.148
    -68.172    20.606

dataArray = table2array(data);

figure
contourf(dataArray, 'ShowText','on')
Ax = gca;
xt = get(Ax, 'XTick');
xtlbl = compose('%.2f',linspace(min(data.X), max(data.X), numel(xt)));
set(Ax, 'XTickLabel',xtlbl)

Note — The x-tick values themselves are not changed, only the x-tick labels change. I am not certain that the same approach would work for the y-axis, since those are much more variable. The best I can do in that respect is to enable the text labels on the contours.

.

[Vishnuvardhan Naidu Tanga]

Thank you. It looks much better to my desired result.

[Star Strider]

As always, my pleasure!

.