How to plot pcolor in matlab

Hello everyone,

i want to plot pcolor plot in matlab but i tried i cannot do it. I add my data here and code also

x  = [13-04-2021 00:00  13-04-2021 01:00  13-04-2021 02:00  13-04-2021 03:00  13-04-2021 04:00] like this till 14-04-2021 23:00:00
y = [10.23  11.16  12.19  13.31  14.54  15.88  17.35  18.96  20.72  22.66  24.77  27.1  29.65  32.45  35.53  38.92  42.65  46.77  51.32]
z = [2.27E+03  3.94E+03  4.48E+03  6.26E+03  3.18E+03  3.78E+03  5.37E+03  5.60E+03  6.35E+03  8.47E+03  1.05E+04  1.05E+04 
    1.36E+04  1.12E+04  8.48E+03  3.96E+03  5.84E+03  4.55E+03  3.65E+03  6.17E+03  7.48E+03  6.98E+03  9.84E+03  1.11E+04  
    5.72E+04  6.90E+04  5.64E+04  4.71E+04  1.94E+04  6.37E+03  6.59E+03  6.89E+03  8.81E+03  9.70E+03  8.11E+03  9.59E+03  
    1.26E+04  1.34E+04  1.69E+04  1.99E+04  2.18E+04  2.62E+04  2.98E+04  9.09E+03  5.16E+03  8.73E+03  3.96E+03  4.95E+03 
    5.16E+03  4.06E+03  4.24E+03  6.17E+03  7.99E+03  8.20E+03  6.68E+03  1.07E+04  1.24E+04  1.36E+04  1.78E+04  1.89E+04]

my x data is in one range and y is in another range and my z data is in different size range.

how to plot that graph?

i hope i will get the answer for this thank you in advance.

[x,y] = meshgrid(x,y);
Pcolor(x,y,z);

[Rik]

You need to find a way to match up your data. It is not clear to me how you are planning to do that. How are you making sure you have as many z values as you have x-y-combinations?

[Walter Roberson]

xd  = {'13-04-2021 00:00' '14-04-2021 23:00'};
xdt = datetime(xd, 'InputFormat', 'dd-MM-yyyy HH:mm');
x = xdt(1) : hours(1) : xdt(2);
y = [10.23  11.16  12.19  13.31  14.54  15.88  17.35  18.96  20.72  22.66  24.77  27.1  29.65  32.45  35.53  38.92  42.65  46.77  51.32];
z = [2.27E+03  3.94E+03  4.48E+03  6.26E+03  3.18E+03  3.78E+03  5.37E+03  5.60E+03  6.35E+03  8.47E+03  1.05E+04  1.05E+04 
    1.36E+04  1.12E+04  8.48E+03  3.96E+03  5.84E+03  4.55E+03  3.65E+03  6.17E+03  7.48E+03  6.98E+03  9.84E+03  1.11E+04  
    5.72E+04  6.90E+04  5.64E+04  4.71E+04  1.94E+04  6.37E+03  6.59E+03  6.89E+03  8.81E+03  9.70E+03  8.11E+03  9.59E+03  
    1.26E+04  1.34E+04  1.69E+04  1.99E+04  2.18E+04  2.62E+04  2.98E+04  9.09E+03  5.16E+03  8.73E+03  3.96E+03  4.95E+03 
    5.16E+03  4.06E+03  4.24E+03  6.17E+03  7.99E+03  8.20E+03  6.68E+03  1.07E+04  1.24E+04  1.36E+04  1.78E+04  1.89E+04];
size(x)

ans = 1×2

1 48

size(y)

ans = 1×2

1 19

size(z)

ans = 1×2

5 12

Your data is all different sizes; we cannot test with it, and we cannot figure out what you are trying to do.

[vignesh mohan]

Hello walter roberson i had attached some reference plot which one i need to try out using this data. I need my x data will come in x-axis and in my y-axis i need my y data from 10 to 50 and my z-axis my z data will come and matrix format.

[vignesh mohan]

Hello Rik i had attached reference graph just have a look then you will get some idea

[vignesh mohan]

Hello Walter sir i had attached some sample data sheet also. my column name should come in my y-axis date will come in my x-axis remaining all will come in z-axis.

i hope you will help me to come out from this sir i tired many way.

Thank you

Answer 1

[Walter Roberson]

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/828415/Book1.xlsx';
T = readcell(filename);
x = [T{2:end,1}];
y = cell2mat(T(1,2:end));
z = cell2mat(T(2:end,2:end));

surf(x, y, z.', 'edgecolor', 'none');

[vignesh mohan]

Hai sir I tried but it shows undefined function or variable 'readcell'. I am using R2016a matlab

[Image Analyst]

Then use xlsread() instead.

[vignesh mohan]

Hai sir I tried T = xlsread(Book1) but it shows error message. Error using xlsread (line 125) File name must be a string

[Rik]

Book1 = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/828415/Book1.xlsx';

%this line is only required if you're downloading the file, instead of
%using a local copy
Book1=websave('Book1.xlsx',Book1);

T = xlsread(Book1)

T = 85×20

1.0e+05 * NaN 0.0001 0.0001 0.0001 0.0001 0.0001 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0003 0.0003 0.0003 0.0004 0.0004 0.0004 0.0005 0.0005 0.4431 0.0151 0.0091 0.0224 0.0156 0.0176 0.0182 0.0349 0.0275 0.0350 0.0307 0.0407 0.0434 0.0530 0.0514 0.0627 0.0736 0.0653 0.0668 0.0679 0.4431 0.0284 0.0228 0.0224 0.0198 0.0248 0.0204 0.0250 0.0293 0.0350 0.0489 0.0350 0.0401 0.0505 0.0486 0.0641 0.0668 0.0708 0.0680 0.0634 0.4431 0.0284 0.0243 0.0286 0.0282 0.0186 0.0212 0.0297 0.0269 0.0238 0.0316 0.0320 0.0428 0.0506 0.0476 0.0574 0.0607 0.0683 0.0654 0.0613 0.4431 0.0132 0.0136 0.0212 0.0187 0.0230 0.0258 0.0256 0.0292 0.0345 0.0356 0.0379 0.0474 0.0501 0.0550 0.0608 0.0634 0.0653 0.0762 0.0631 0.4431 0.0290 0.0263 0.0266 0.0250 0.0236 0.0340 0.0262 0.0310 0.0284 0.0318 0.0448 0.0415 0.0400 0.0548 0.0479 0.0628 0.0604 0.0693 0.0702 0.4431 0.0398 0.0349 0.0473 0.0260 0.0274 0.0342 0.0430 0.0362 0.0311 0.0369 0.0283 0.0477 0.0422 0.0572 0.0577 0.0659 0.0640 0.0640 0.0718 0.4431 0.0170 0.0182 0.0149 0.0093 0.0204 0.0251 0.0236 0.0263 0.0233 0.0261 0.0385 0.0418 0.0479 0.0545 0.0543 0.0587 0.0628 0.0654 0.0660 0.4431 0.0208 0.0288 0.0099 0.0229 0.0123 0.0181 0.0303 0.0288 0.0335 0.0389 0.0406 0.0340 0.0482 0.0491 0.0525 0.0542 0.0564 0.0611 0.0685 0.4431 0.0132 0.0152 0.0224 0.0156 0.0257 0.0235 0.0336 0.0217 0.0310 0.0375 0.0367 0.0398 0.0448 0.0481 0.0489 0.0546 0.0592 0.0676 0.0619

[vignesh mohan]

Thank you rik

[vignesh mohan]

When I entered y=cell2mat(T(1,2:end));it shows error message Error using cell2mat (line42) You cannot subscript a table using only one subscript. Table subscripting requires both row and variable subscrpts. I don't know next what I have to do ????

[Image Analyst]

Book1 needs to be a string, and apparently it's not. Try

fullFileName = fullfile(pwd, 'Book1.xlsx');
if isfile(fullFileName)
    [numbers, strings, T] = xlsread(fullFileName);
else
    warningMessage = sprintf('File not found:\n%s', fullFileName);
    uiwait(errordlg(warningMessage));
    return;
end

T will be the raw cell array while numbers is just the numbers (with nan wherever there is a string in the matrix), and strings is a cell array with just the text cells.

[vignesh mohan]

I tried sir but it shows Undefined function 'isfile' for input arguments of type 'char'

[Image Analyst]

You must have a really old version. Use exist() instead:

if exist(fullFileName, 'file')

[vignesh mohan]

Thank you Image Analyst

when i entered surf(x, y, z.', 'edgecolor', 'none'); it show errow message.

Error using matlab.graphics.chart.primitive.Surface/set

Invalid parameter/value pair arguments.

Error in matlab.graphics.chart.internal.ctorHelper (line 6)

set(obj, pvpairs{:});

Error in matlab.graphics.chart.primitive.Surface

Error in surf (line 126)

hh = matlab.graphics.chart.primitive.Surface(allargs{:});

The above Error message is pop up.

[vignesh mohan]

Full code i showed you

T = Book1;
fullFileName = fullfile(pwd, 'Book1.xlsx');
if exist(fullFileName, 'file')
          [numbers, strings, T] = xlsread(fullFileName);
else
    warningMessage = sprintf('File not found:\n%s', fullFileName);
    uiwait(errordlg(warningMessage));
    return;
end
x = [T{2:end,1}];
y = cell2mat(T(1,2:end));
z = cell2mat(T(2:end,2:end));
surf(x, y, z.', 'edgecolor', 'none');

Now i am standing in last line of the code. Help me to figure it out. Thank you so much i advance.

[Walter Roberson]

surf(x, y, z.');

[vignesh mohan]

Hai sir

Again i got same error

Error using matlab.graphics.chart.primitive.Surface/set

Invalid parameter/value pair arguments.

Error in matlab.graphics.chart.internal.ctorHelper (line 6)

set(obj, pvpairs{:});

Error in matlab.graphics.chart.primitive.Surface

Error in surf (line 126)

hh = matlab.graphics.chart.primitive.Surface(allargs{:});

[Walter Roberson]

please post your current code

[vignesh mohan]

T = Book1;
fullFileName = fullfile(pwd, 'Book1.xlsx');
if exist(fullFileName, 'file')
          [numbers, strings, T] = xlsread(fullFileName);
else
    warningMessage = sprintf('File not found:\n%s', fullFileName);
    uiwait(errordlg(warningMessage));
    return;
end
x = [T{2:end,1}];
y = cell2mat(T(1,2:end));
z = cell2mat(T(2:end,2:end));
surf(x, y, z.');

Error Message

Error using matlab.graphics.chart.primitive.Surface/set

Invalid parameter/value pair arguments.

Error in matlab.graphics.chart.internal.ctorHelper (line 6)

set(obj, pvpairs{:});

Error in matlab.graphics.chart.primitive.Surface

Error in surf (line 126)

hh = matlab.graphics.chart.primitive.Surface(allargs{:});

This is my current code sir

Till z the code went good i think i didnt receive any Error message

But when i enter Surf code i got the error

[Walter Roberson]

The code works when I try it in R2016a on my system.

To debug this, give the commands

dbstop in matlab.graphics.chart.internal.ctorHelper
surf(x, y, z.')

The code should run, but stop in ctorHelper.m . When it stops, please show us the value of the variable named pvpairs -- and also please show us class(obj)

[vignesh mohan]

Hai sir,

pvpairs show ['Parent' 1x1 Axes

'''21-04-202121-04-2021 00:15:0021-04-2021 00:30:0021-04-2021 00:45:0021-04-2021 01:00:0021-04-2021 01:15:0021-04-2021 01:30:0021-0...'' <Preview truncated at 128 characters>' 1x19 double

19x84 double]

obj shows 1 x 1 Surface

After entered surf(x,y,z.') it shows below code

5      if ~isempty(pvpairs)
K>> 

[vignesh mohan]

Function:

function ctorHelper(obj, pvpairs)

%   Copyright 2014-2015 The MathWorks, Inc.

if ~isempty(pvpairs)
    set(obj, pvpairs{:});
end
end

[Walter Roberson]

Please show the output for

which -all surf

Your pvpairs are not even in the same order that I would expect for your release. I would expect

'XData'    [1x84 double]    'YData'    [1x19 double]    'ZData'    [19x84 double]    'Parent'    [1x1 Axes]

[vignesh mohan]

>> surf(x, y, z.')
5      if ~isempty(pvpairs)
K>> which -all surf
C:\Program Files\MATLAB\R2016a\toolbox\matlab\graph3d\surf.m
C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbctools\@sweepset\surf.m  % Shadowed sweepset method
K>> 

It came like this Sir.

once when i entered above code, it will remove all x,y,z values from my workspace and shows only obj,pvpairs.

[Andebo Waza]

Dear all,

I need your help. I have wind data in 2D (Height, Time). I want to plot a 60-minute average data, and I want to do that using pcolor plot. I managed to generate the plot with the original data (30 min), but failed to do it on a 60-min average. I am relatively new to netcdf data. Any help is greatly appreciated!

Here is my code for original data:

clear all
close all
clc
ncid = netcdf.open('wl_geomar_CSM_l2_v04_20240916.nc','NC_NOWRITE');
filename = ncinfo('wl_geomar_CSM_l2_v04_20240916.nc');
disp(filename);
ncdisp('wl_geomar_CSM_l2_v04_20240916.nc');
longitude = ncread('wl_geomar_CSM_l2_v04_20240916.nc','lon');
latitude = ncread('wl_geomar_CSM_l2_v04_20240916.nc','lat');
time = ncread('wl_geomar_CSM_l2_v04_20240916.nc','time');
epoch = datetime(1970, 01, 01)
T = epoch + seconds(time)
u = ncread('wl_geomar_CSM_l2_v04_20240916.nc','u');
v = ncread('wl_geomar_CSM_l2_v04_20240916.nc','v');
wspeed = ncread('wl_geomar_CSM_l2_v04_20240916.nc','wspeed');
height = ncread('wl_geomar_CSM_l2_v04_20240916.nc','height');
u_mean=sqrt(u.^2+v.^2+wspeed.^2);
mymap=pcolor(T,height,u_mean);
shading interp
h= colorbar
caxis([0 20])
drawnow
ylabel(h,'Mean wind speed (m/s)');
grid on
xlabel('Time (UTC)')
ylabel('Height (m)')
xtk=xticks;

I would be happy to provide you the data if needed.

[Steven Lord]

What does "failed to do it on a 60-min average" mean in this context?

• Do you receive warning and/or error messages? If so the full and exact text of those messages (all the text displayed in orange and/or red in the Command Window) may be useful in determining what's going on and how to avoid the warning and/or error.
• Does it do something different than what you expected? If so, what did it do and what did you expect it to do?
• Did MATLAB crash? If so please send the crash log file (with a description of what you were running or doing in MATLAB when the crash occured) to Technical Support so we can investigate.

[Walter Roberson]

TT = timetable(T, u, v, wspeed, height);
TT60 = retime(TT, minutes(60));
u_mean60 = sqrt(TT60.u.^2 + TT60.v.^2);
mymap60 = pcolor(TT60.T, TT60.height, TT60.u_mean60);

[Andebo Waza]

Dear@Walter Roberson,

Thank you so much. Here is the error message I am getting after I tried to plot it using your code:

" Error using timetable (line 328)

All table variables must have the same number of rows."

[Walter Roberson]

Please show the output for

whos T u v wspeed height

[Sebastian]

@Walter Roberson,

Here is the output:

>> whos T u v wspeed height

Name Size Bytes Class Attributes

T 48x1 384 datetime

height 99x1 792 double

u 99x48 38016 double

v 99x48 38016 double

wspeed 99x48 38016 double

[Andebo Waza]

@Walter Roberson, I can also share the data with you. Just let me know if you need it.

[Walter Roberson]

u = u.';
v = v.';
wspeed = wspeed.';

TT = timetable(T, u, v, wspeed);
TT60 = retime(TT, minutes(60));
u_mean60 = sqrt(TT60.u.^2 + TT60.v.^2);
mymap60 = pcolor(TT60.T, height, TT60.u_mean60);

[Andebo Waza]

Dear @Walter Roberson

I am still getting an error message, "Error using timetable/retime (line 142)

All input timetables must have row times with the same data type as target time

vector."

[Walter Roberson]

Is that error message coming from the retime() call?

If so, try

TT60 = retime(TT, 'regular', 'linear', 'timestep', minutes(60));

[Andebo Waza]

Dear @Walter Roberson, Thank you so much. I made a little modification and it works now.

Here is the final one:

u = u.';
v = v.';
wspeed = wspeed.';
TT = timetable(T, u, v, wspeed);
TT60 = retime(TT, 'regular', 'linear', 'timestep', minutes(60));
%TT60 = retime(TT, minutes(60));
u_mean60 = sqrt(TT60.u.^2 + TT60.v.^2+TT60.wspeed.^2);
mymap60 = pcolor(TT60.T, height, u_mean60').

[Andebo Waza]

Dear @Walter Roberson,

Thank you again for helping me. I am now trying to write another code for the same dataset (this time I have the python code but I need to trasnlate that into Matlab code as I do not use Python). Could you please help me with is part too? I really apperciate your help.

Here is the python that I need to re-write in Matlab.

#filter signals for plotting, which are only marginally above molecular signal

bsc_mask = bsc_par_prl < np.repeat(np.reshape(1.5*mol_bsc, (1,len(mol_bsc))), att_bsc_crs_avg.shape[0], axis=0)

depol_par_masked = np.ma.array(depol, mask=bsc_mask)

bsc_par_masked = np.ma.array(bsc_par_prl, mask=bsc_mask)

[Walter Roberson]

Sorry, I do not know how to read python. In particular I do not know the meaning of np.ma.array especially in conjugation with the mask= parameter.

[Andebo Waza]

@Walter Roberson, No worries. I managed to write the code.