Scatter plot - different colour marker for night and day

Hi,

I have hourly radiation data for the whole year (8760 values in total) have used scatter plots to plot this data. My time data is in 'dd-mm-yyyy HH:MM:SS' format and I used startdate/enddate and linspace for this. I was hoping to colour the markers by the time of day e.g. red for 0600-1800 and blue for 1800-0600 but have no idea how to do this as am relatively new to Matlab.

Does anyone know how to do this?

Thanks

[Ali]

if true
--------------------------------------------------- code start
This is an example for your case 
Input is "Input_Data", two dimension matrix 
Marker_Counter=1;
   figure6=figure;
   Markers = {'+','o','*','x','v','d','^','s','>','<'};
   for i=1:10:size(Input_Data,1)
    TPR=Input_Data(i:i+9,7);
    FPR=Input_Data(i:i+9,8);
plot(FPR,TPR,strcat('-',Markers{Marker_Counter}));
Marker_Counter=Marker_Counter+1;   
hold on
   end
plot([0.5 1],[0.5 1],'--');
legend('Minpts = 100','Minpts = 200','Minpts = 300','Minpts = 400','Minpts = 500','Minpts = 600','Minpts = 700','Minpts = 800','Minpts = 900','Minpts = 1000','','Location','SouthEast');
xlabel('FPR or (1-Specificity)','FontSize',12,'FontWeight','bold'); ylabel('TPR or Spensitivity)','FontSize',12,'FontWeight','bold');
title('ROC Space');
close(gcf);
-------------------------------------------- code end
end
--------------------------------------- picture link preview

Answer 1

[dpb]

Presuming you converted to datetime array for the times, then

Well, here, let's just build a sample...

>> t=datetime(2001,1,1,[0:365*24].',0,0); t(end)=[];  % 8760-long hourly datetime series
>> iday=iswithin(hour(t),6,18)+1;  % vector of day/night indices 1==>night, 2-->day
>> [min(iday) max(iday)]           % show the above is so...
ans =
   1     2
>> c=[[0 0 1];[1 0 0]];              % colors blue and red as members of 2-element array
>> clr=c(iday,:);
>> whos clr
Name         Size            Bytes  Class     Attributes
clr       8760x3             70080  double              
>>

Now just pass the clr array to scatter and voila! you'll get the two colors.

What would be kinda' cute here would be to find a sunrise/sunset calculator and tie the colors to it instead of just fixed hours.

scatter only takes a vector of RGB triplets; a thread came up just a week ago or so where I pointed out it would be useful to be able to use the named colors in same way. A TMW employee agreed would be worthy of enhancement request; don't know if he picked it up or not and did so; I'd done it years and years ago.

Oh, almost forgot -- iswithin is a utility routine of mine; just "syntactic sugar" for the double-comparison. It's just

>> type iswithin

function flg=iswithin(x,lo,hi)
% returns T for values within range of input
% SYNTAX:
%  [log] = iswithin(x,lo,hi)
%      returns T for x between lo and hi values, inclusive

    flg= (x>=lo) & (x<=hi);
  >>

one can always just write the conditional expression, but it can get very messy in indexing or other more complex expressions so the factorization often makes for much cleaner-looking user code.

ADDENDUM

I just remembered there's a new TMW function isbetween that does same thing for datetime values. Oh, but hour returns a double array and it can't handle them and doesn't seem to have options for the intervals of other than dates. So, the above seems the route; doesn't look like the datetime class does anything else for you here.