scatter plot with different radius for different range of values

*I have three column vectors , Latitude ,longitude,magnitude of earthquake (338x1),

*so I need to make a scatter plot (X axis :longitude,Y axis :latitude),

• But the radius of the scatter should be same for particular range of magnitude,like mag<3,3=<mag<4,4<=mag<5..... 9=<mag<10.

So I should read the magnitude first and plot the scatter for corresponding latitude and longitude with radius according to the magnitude range

can anyone help me with this?

Answer 1

[michio]

I know it's not as elegant as we hope, but one way is to create a new variable that represents the radius and then use scatter function. logical indexing could perform better than using for-loop.

See. http://blogs.mathworks.com/loren/2013/02/20/logical-indexing-multiple-conditions/

The following is one example. Hope it helps.

[x,y] = meshgrid(1:10,1:10);
% Magnitude with random number ranging from 0 to 10.
mag = rand(1,100)*10;

idx1 = mag < 3;
idx2 = (3 <= mag) & (mag < 5);
idx3 = (5 <= mag) & (mag < 8);
idx4 = 8 <= mag;

magSize = zeros(size(mag));
magSize(idx1) = 1;
magSize(idx2) = 9;
magSize(idx3) = 25;
magSize(idx4) = 49;

scatter(x(:),y(:),magSize);

[vivek GB]

     title_name=input('Please enter period in years?\n','s')  
%input for the title of the plot
for i=1:length(lat); %lat= latitude
idx1 = mag < 3;
idx2 = (3 >= mag) & (mag < 4);   %mag=magnitude 
idx3 = (4 >= mag) & (mag < 5);
idx4 = (5 >= mag) & (mag < 6);
idx5 = (6 >= mag) & (mag < 7);
idx6 = (7 >= mag) & (mag < 8);
idx7 = (8 >= mag) & (mag < 9);
idx8 = (mag>9);                  
end

magSize = zeros(size(lat));
magSize(idx1) = 10;
magSize(idx2) = 20;
magSize(idx3) = 30;
magSize(idx4) = 40;
magSize(idx5) = 50;
magSize(idx6) = 60;
magSize(idx7) = 70;
magSize(idx8) = 80;
scatter(lon,lat,magSize,'fill','MarkerEdgeColor',[0 .5 .5])%lon=longitude
hold on;
xlim([74 82]);ylim([28 35]);
xlabel('long');ylabel('latitude');
title(sprintf('%s lat vs lon :mag',title_name))

%% * _ I tried your code ( with my own improvement because it was showing some minor error) ,but still i stuck with this problem ,it seems like i only getting the scatters with same radius!! please help me to improve my code_!!* "Is it that the wrong use of '<' ,'>' sign?

[michio]

Hmm, I would first make sure if magSize does have values as you intended. Could you try the following to see the number of entries from each maginitude category.

sum(idx1)
sum(idx2)

and so on?

[vivek GB]

yeah magSize do have values as i intended ,i made sure that. magSize =

     0
    10
    10
    30
    30
    50
    30
    10
    10
    30
    10
    30
    70
    30
    30
    30
    10
    10
    10
  so on........

i used the below code to plot the scatter in different color for the each element in magSize have a specific value,but it seems to be loop doesnt working at all

please give your suggestion

figure
for i=1:length(lat)
if (magSize(i)==10)
  scatter(lon,lat,magSize,'fill','MarkerEdgeColor','k','MarkerFaceColor','r');
  hold on;
elseif magSize(i)==30
  scatter(lon,lat,magSize,'fill','MarkerEdgeColor','k','MarkerFaceColor','y');
  hold on;
elseif magSize(i)==50
  scatter(lon,lat,magSize,'fill','MarkerEdgeColor','k','MarkerFaceColor','m');
  hold on;
elseif magSize(i)==70
  scatter(lon,lat,magSize,'fill','MarkerEdgeColor','k','MarkerFaceColor','c');
  hold on;
elseif magSize(i)==80
  scatter(lon,lat,magSize,'fill','MarkerEdgeColor','k','MarkerFaceColor','g');
  hold on;
elseif magSize(i)==95
  scatter(lon,lat,magSize,'fill','MarkerEdgeColor','k','MarkerFaceColor','b');
  hold on;
elseif magSize(i)==105
  scatter(lon,lat,magSize,'fill','MarkerEdgeColor','r','MarkerFaceColor','k');
  hold on;
elseif magSize(i)==115
  scatter(lon,lat,magSize,'d','fill','MarkerEdgeColor','k','MarkerFaceColor','r');
  hold on;
elseif magSize(i)==115
  scatter(lon,lat,magSize,'x','MarkerFaceColor','r');
  hold on;
end
end

[michio]

The above script calls scatter function for every point in each case so I do not think it's what you intended. It would be great if I could reproduce your situation at my end, it's hard to make a speculations..

Anyways, the script in my answer shows some variation in marker sizes in your side, doesn't it?

I think it's also worth pointing out that the units for the marker area is points squared. So the magSize should represent the area of each marker, not the diameter of the marker.

Having said that

scatter(lon,lat,magSize.^2,'fill','MarkerEdgeColor',[0 .5 .5])

makes any changes?

[vivek GB]

yeah, now I can plot scatters with different size according to magSize,but I can't put different colour according to scatters size(for that I tried to use "If.....else"),how can I do that?

[michio]

The above script of yours overwrites everything at every scatter function call. One way to do this is

scatter(lon(idx1),lat(idx1),magSize(idx1),'fill','MarkerEdgeColor','k','MarkerFaceColor','r')
hold on
scatter(lon(idx2),lat(idx2),magSize(idx2),'fill','MarkerEdgeColor','k','MarkerFaceColor','y')
scatter(lon(idx3),lat(idx3),magSize(idx3),'fill','MarkerEdgeColor','k','MarkerFaceColor','m')
scatter(lon(idx4),lat(idx4),magSize(idx4),'fill','MarkerEdgeColor','k','MarkerFaceColor','c')
scatter(lon(idx5),lat(idx5),magSize(idx5),'fill','MarkerEdgeColor','k','MarkerFaceColor','g')

and so on instead of using if else. If you use the scatter(x,y,a,c) syntax, where c specifies the circle color, it can be done by one scatter call. But if the number of category is small enough, the above way could be easier to understand.

Using the fact that scatter function accepts color as three column matrix of RGB triplets, another working example follows.

[x,y] = meshgrid(1:10,1:10);
% Magnitude with random number ranging from 0 to 10.
mag = rand(1,100)*10;
idx1 = mag < 3;
idx2 = (3 <= mag) & (mag < 5);
idx3 = (5 <= mag) & (mag < 8);
idx4 = 8 <= mag;
magSize = zeros(size(mag));
magSize(idx1) = 1;
magSize(idx2) = 9;
magSize(idx3) = 25;
magSize(idx4) = 49;

magColor = zeros(length(mag),3);
magColor(idx1,:) = repmat([1 1 0],[sum(idx1),1]);
magColor(idx2,:) = repmat([1 0 1],[sum(idx2),1]);
magColor(idx3,:) = repmat([0 1 1],[sum(idx3),1]);
magColor(idx4,:) = repmat([1 0 0],[sum(idx4),1]);

scatter(x(:),y(:),magSize,magColor,'fill');

[vivek GB]

Thank you very much Michio,,you are such a life saver!!Got it

[michio]

I'm glad to know it helped :)