MATLAB Answers

2D line plot xy with color from z variable

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Ann
Ann on 9 Feb 2021
Commented: Mathieu NOE on 11 Feb 2021
Hi everyone,
I have an abundance of data in excel (556873 rows). Data can be get here Data 365 days .
x=TIME, y=S4, z=PRN.
I am trying to make a 2D line plot but I want it to vary in color by z variable. FYI, z variable contain a number from 1-32. Meaning that the data will be as example below:
DAY TIME PRN S4
1 0.00138888888888889 4 0.0668452919508921
1 0.00138888888888889 2 0.0559732347198194
1 0.00208333333333333 4 0.0491661308727868
1 0.00208333333333333 28 0.0379869911285429
1 0.00208333333333333 10 0.0203279197164885
1 0.00208333333333333 2 0.0556284592749356
Here is what I had try but it turns out as one color line plot because I don't know how to custom the line color based on z (PRN).
clear
clc
%___Read data___%
data = readtable("Param_365.xlsx");
%___Define variable___%
%DAY = data.DAY;
TIME = data.TIME;
S4 = data.S4;
PRN = data.PRN;
%___Plot scatter 2-D___%
plot(TIME, S4)
%___Axes properities___%
title('Time variation of the S_4 index in 2014');
datetick('x', 'HH');
xlabel('Coordinated Universal Time, UTC (hr)');
ylabel('Amplitude scintillation, S_4');
hold all
I did scatter before and it works but
clear
clc
%___Read data___%
data = readtable("Param_365.xlsx");
%___Define variable___%
%DAY = data.DAY;
TIME = data.TIME;
S4 = data.S4;
PRN = data.PRN;
%___Plot scatter 2-D___%
scatter(TIME, S4, 10, PRN,'filled')
colormap(jet(32))
caxis([1 32]);
colorbar('YTick', [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32]);
%___Axes properities___%
title('Time variation of the S_4 index in 2014');
datetick('x', 'HH');
xlabel('Coordinated Universal Time, UTC (hr)');
ylabel('Amplitude scintillation, S_4');
hold all
But my data will be more appropriate if in the form of line plot as below:
I hope anyone could help me on this because I tried few tricks but it failed. Thank you in advanced.

Answers (3)

Mathieu NOE
Mathieu NOE on 9 Feb 2021
hello
my 2 cents suggestion
%___Read data___%
data = readtable("Classeur1.xlsx");
%___Define variable___%
%DAY = data.DAY;
TIME = str2double(data.TIME);
S4 = str2double(data.S4);
PRN = data.PRN;
% %___Plot scatter 2-D___%
% scatter(TIME, S4, 10, PRN,'filled')
%
% colormap(jet(32))
% caxis([1 32]);
% colorbar('YTick', [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32]);
% %___Axes properities___%
% title('Time variation of the S_4 index in 2014');
% datetick('x', 'HH');
% xlabel('Coordinated Universal Time, UTC (hr)');
% ylabel('Amplitude scintillation, S_4');
% hold all
% // modified jet-colormap
n = length(PRN);
cd = [uint8(jet(n)*255) uint8(ones(n,1))].' %'
p = plot(TIME, S4, 'LineWidth',4);
title('Time variation of the S_4 index in 2014');
datetick('x', 'HH');
xlabel('Coordinated Universal Time, UTC (hr)');
ylabel('Amplitude scintillation, S_4');
caxis([1 32]);
colormap(jet(32));
cbv=colorbar('v');
set(cbv,'YTick',[1:32],'TickLabels',cellstr(num2str((1:32)')))
drawnow
set(p.Edge, 'ColorBinding','interpolated', 'ColorData',cd)
  6 Comments
Mathieu NOE
Mathieu NOE on 11 Feb 2021
Glad it helps !
I don't have that much merit , simply used the info I found from Yair's undocumented-matlab site
now maybe you could do this plot for a longer period in one graph but this needs first to do some averaging vs time (1 hour basis ? );

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Iuliu Ardelean
Iuliu Ardelean on 9 Feb 2021
Try this:
x = 1:100;
y = rand(1, 100);
z = randsample(32, 100, true);
figure
hold on
for i = 1:32
plot(x(z==i), y(z==i),'-') % you can assign colors here as you want
% you can also try different markers maybe, if lines are no good?
end
hold off
  4 Comments
Ann
Ann on 11 Feb 2021
@Iuliu Ardelean , thanks for your assistance! Your code works with my real data here: Data 365 days . But probably because of the data is too much so it looks inconvenient in the form of graph. But I sincerely thanks for the help.

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Walter Roberson
Walter Roberson on 11 Feb 2021
There are three approaches:
  1. use a surface plot and control edge color
  2. use a patch() and control edge color.
  3. use some advanced and obscure internal undocumented properties
There are a couple of File Exchange contribution you can use. One of them is https://www.mathworks.com/matlabcentral/fileexchange/19476-colored-line-or-scatter-plot
Yair's undocumented-matlab site shows how to use the internal undocumented properties.

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