2D line plot xy with color from z variable

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.

[KALYAN ACHARJYA]

@Ann Where is the z variable here?

[Ann]

Hi @KALYAN ACHARJYA, Z refer to PRN as stated above.

Answer 1

[Mathieu NOE]

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)

[Ann]

Hi @Mathieu NOE, thanks for the response. The graphically looks good but It turns out in one color as below and not as expected in vary colors as the colorbar.

[Mathieu NOE]

hello

maybe I misunderstood the problem

do you intend to plot multiple lines and one line = one color

or , as I guessed from the first input data, you wanted to plot one single line and the sgements between the points must have gradually changing color according to a z value ?

NB the initial data given only shows one x, y pair for one PRN value so I cannot draw a line with that single point

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

maybe you should share the actual data to display (from fig above)

[Ann]

Basically there will be too many lines but I want it to vary in color by the variable Z (PRN).

The data file is big you may donwload it here Data 365 days .

I am expecting the graph is going to be something like in S_4 graph below (ignore the other subplots):

[Mathieu NOE]

hello

see my code below ; I plotted each day separatly (1 figure per day) otherwise the plot is unreadable

this is the visual result :

but I limited myself to the first 7 days otherwise my matlab would take forever to plot + 300 figures;

%___Read data___%
data = readtable("Param_365.xlsx");
%___Define variable___%
DAY = data.DAY;
TIME = data.TIME;
S4 = data.S4;
PRN = data.PRN;

N = 32; % color axis max level (colorbar)

for ci = 1: 7 %max(DAY)
    ind =find(DAY == ci);
    x = TIME(ind); % to get it in hours 
    y = S4(ind);
    z = PRN(ind);
    figure(ci),
    h = plot(x,y,'-'); % capture the line handle when you plot it
    datetick('x', 'HH');
    xlabel('Coordinated Universal Time, UTC (hr)');
    ylabel('Amplitude scintillation, S_4');
    title([' Day : ' num2str(ci) ]);
    caxis([0 N]);
    cd = colormap(jet(N+1)); % take your pick (doc colormap)
    cd = interp1(linspace(0,N,length(cd)),cd,z); % map color to z values
    cd = uint8(cd'*255); % need a 4xN uint8 array
    cd(4,:) = 255; % last column is transparency
    cbv=colorbar('v');
    set(cbv,'YTick',[0:N],'TickLabels',cellstr(num2str((0:N)')))
    drawnow
    set(h.Edge,'ColorBinding','interpolated','ColorData',cd)
end

[Ann]

@Mathieu NOE Woah! Yours is perfectly perfect for my daily observations. Maybe for my question it is kinda impossible to do a year observation in one graph. Thanks for your help, bud!

[Mathieu NOE]

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 ? );

Answer 2

[Iuliu Ardelean]

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

[Ann]

Hi @Iuliu Ardelean , thank you for your attempt to answer. I did changes on the code:

clear
clc

data = readtable("Param_365.xlsx");

x = data.TIME;
y = data.S4;
z = data.PRN;

figure
hold on
for i = 1:32
    plot(x(z==i), y(z==i), 'LineWidth',2)
end
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 off

But it resulting as below which is looks good. Basically, how am I going to make the line in the color variation as in colorbar?

Expected line in this color variation (ignore the subplot, look at the S_4 plot):

[Iuliu Ardelean]

Hey Ann

I see -- I would probably try using a legend

e.g.

[Iuliu Ardelean]

Or did you mean, how are you going to find the colors from inside S4 subplot?

If that's what you meant then it's pretty easy. Type this in command window:

>> jet(32)

So, your code will look like this:

x = 1:100;
y = rand(1, 100);
z = randsample(32, 100, true);
colors = jet(32);
figure
hold on
for i = 1:32
    plot(x(z==i), y(z==i), 'LineWidth',2, 'Color', colors(i,:)) % you can assign colors here as you want
                               % you can also try different markers maybe, if lines are no good?
end
hold off

And your image will look like this:

[Ann]

@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.

Answer 3

[Walter Roberson]

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.