Setting x axis in hh:mm format for plotting

Question

Sreeraj T 2020-6-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/550467-setting-x-axis-in-hh-mm-format-for-plotting

评论： Sreeraj T 2020-6-19

I have a code which goes like this:

clc;clear;close all
%% 
Time=linspace(16.8,17.8,230400)';
Field=linspace(50,145,230400)';
figure('units','normalized','outerposition',[0 0 1 1])
plot(Time,Field)
%% 
figure('units','normalized','outerposition',[0 0 1 1]) 
hammng_wndw_size=4096;
window=hamming(hammng_wndw_size); %window size
noverlap=512; % the noverlaps its the no. of points for repeating the window
nfft=4096; %size of fft
fs=32; %sampling freq
[Sp,F,T,P]=spectrogram(Field,window,noverlap,nfft,fs,'yaxis');
T_forspectrogrm=T./3600+Time(1);
surf(T_forspectrogrm,F,10*log10(P),'edgecolor','none','FaceColor','interp');
axis tight;ylim([0 4]);view(0,90);
colormap(jet);colorbar;

The result of this plot is these two figures:

The xaxis is time and y axis is some other quantity, lets say field. Now, when I plotting, the x axis starts from 16.8 to 17.8 for first figure and 16.8 and 18.8 for second figure. This actually corresponds to 16:48:00 to 17:48:00 and similarly for the second one. How do I have to modify the program to convert the x-axis into hh:mm format do this job?

I tried in this fashion

TimeInReqFrmat=datestr(Time(:,1),'HH:MM:SS');

but this gives me a string of characters.

I am using Matlab 2016a.

Thanks in advance

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Answer 1

Mehmed Saad 2020-6-18

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https://ww2.mathworks.cn/matlabcentral/answers/550467-setting-x-axis-in-hh-mm-format-for-plotting#answer_453318

在 MATLAB Online 中打开

The Dumb Method

clc;clear;close all
Time=linspace(16.8,17.8,230400)';
Field=linspace(50,145,230400)';
figure('units','normalized','outerposition',[0 0 1 1])
plot(Time,Field)
%% Edited by Mehmed
%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
ax =gca; 
ax.XTickLabel=datestr(hours(ax.XTick),'HH:MM:SS');% Edited by Mehmed
%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
figure('units','normalized','outerposition',[0 0 1 1]) 
hammng_wndw_size=4096;
window=hamming(hammng_wndw_size); %window size
noverlap=512; % the noverlaps its the no. of points for repeating the window
nfft=4096; %size of fft
fs=32; %sampling freq
[Sp,F,T,P]=spectrogram(Field,window,noverlap,nfft,fs,'yaxis');
T_forspectrogrm=T./3600+Time(1);
surf(T_forspectrogrm,F,10*log10(P),'edgecolor','none','FaceColor','interp');
axis tight;ylim([0 4]);view(0,90);
colormap(jet);colorbar;
%% Edited by Mehmed
%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
ax =gca;
ax.XTickLabel=datestr(hours(ax.XTick),'HH:MM:SS');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%

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Mehmed Saad 2020-6-19

在 MATLAB Online 中打开

You can also try this

% Changing time to duration directly
Time =duration(hours(linspace(16.8,17.8,230400)'),'format','hh:mm:ss');
Field=linspace(50,145,230400)';
figure('units','normalized','outerposition',[0 0 1 1])
plot(Time,Field)

Sreeraj T 2020-6-19

Mehmed Saad, thank you..

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Answer 2

Ajith Krishna Kanduri 2020-6-18

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https://ww2.mathworks.cn/matlabcentral/answers/550467-setting-x-axis-in-hh-mm-format-for-plotting#answer_453330

Hi Sreeraj,

Please refer to the documentation of datestr function (https://in.mathworks.com/help/matlab/ref/datestr.html). I think the arguments you are passing into the constuctor doesn't match any syntax. You can either write another function that can change Time array as you mentioned and then pass that string array into the constructor or instead you could directly create a dateformat array that could be used.