Marker size based on value

Question

Gareth Maver 2016-2-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/268595-marker-size-based-on-value

评论： Shai Katz 2020-11-20

采纳的回答： Mike Garrity

CenUS_ZMAP.txt

在 MATLAB Online 中打开

I am wanting to recreate the following plot but with the size of the dots changing based on the magnitude (mag) value.

Here is my code so far:

data = load(filename) ;
  long = data(:,1) ;
  lati = data(:,2) ;
  year = data(:,3) ;
  mag = data(:,6) ;    
for i = 1:length(mag)
  if mag(i) < 3.0
      mag(i) = NaN ;
      lati(i) = NaN ;
      long(i) = NaN ;
  end
end
new_lati = zeros(length(lati),1) ;
new_long = zeros(length(long),1) ;
new_lati1 = zeros(length(lati),1) ;
new_long1 = zeros(length(long),1) ;
for i = 1:length(lati) 
  if new_lati(i) == 0 
      new_lati(i) = NaN ;
  end
  if new_long(i) == 0 
      new_long(i) = NaN ;
  end 
  if new_lati1(i) == 0 
      new_lati1(i) = NaN ;
  end
  if new_long1(i) == 0 
      new_long1(i) = NaN ;
  end
  if year(i) > 2008
      new_lati(i) = lati(i) ;
      new_long(i) = long(i) ;
  end
  if year(i) > 2013
      new_lati1(i) = lati(i) ;
      new_long1(i) = long(i) ;
  end
end
latlim = [33 39];
lonlim = [-102 -94];
figure
ax = usamap(latlim,lonlim) ;
set(ax, 'Visible', 'off')
states = shaperead('usastatehi',...
      'UseGeoCoords', true, 'BoundingBox', [lonlim', latlim']);
geoshow(ax, states, 'FaceColor', [1.0 0.9 0.7])
lat = [states.LabelLat];
lon = [states.LabelLon];
tf = ingeoquad(lat, lon, latlim, lonlim);
hold on
h1 = linem(lati, long, 'LineStyle','none', 'LineWidth',2, 'Color','b', ...
  'Marker','.', 'MarkerSize',10) ;
h2 = linem(new_lati, new_long, 'LineStyle','none', 'LineWidth',2, 'Color','[0.0 0.8 0.3]', ...
  'Marker','.', 'MarkerSize',10) ; 
h3 = linem(new_lati1, new_long1, 'LineStyle','none', 'LineWidth',2, 'Color','r', ...
  'Marker','.', 'MarkerSize',10) ;

I have tried using scatterm instead of linem, however didnt know how to keep the corresponding colours.

Any help would be appreciated. Thanks

Gareth

3 个评论
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Gareth Maver 2016-2-17

Sorry. I have attached the data now.

Stephen23 2016-2-17

编辑：Stephen23 2016-2-17

在 MATLAB Online 中打开

That code would be much more efficient with logical indices rather than using slow and bulky loops:

filename = 'CenUS_ZMAP.txt';
data = load(filename);
%
long = data(:,1);
lati = data(:,2);
year = data(:,3);
mag  = data(:,6);
%
idx = mag<3.0;
long(idx) = NaN;
lati(idx) = NaN;
year(idx) = NaN;
mag(idx)  = NaN;
%
new_lati = lati;
new_long = long;
new_lati(year<=2008) = NaN;
new_long(year<=2008) = NaN;

Even better would be to avoid using those NaN's, and simply keep only the values that you wish to plot:

idy  = data(:,6)>=3.0;
long = data(idy,1);
lati = data(idy,2);
year = data(idy,3);
mag  = data(idy,6);
%
new_lati = lati(year>2008);
new_long = long(year>2008);
new_lati1 = lati(year>2013);
new_long1 = long(year>2013);

That is much simpler, much tidier, and much faster to run than using loops to move values one-at-a-time. Although beginners seem to love using loops, there are much simpler and more efficient ways to program in MATLAB, such as code vectorization. MATLAB is a high-level language, it is not Python or C++, so leave those slow and ugly loops behind you and learn to use MATLAB's fast and efficient indexing. More tips for MATLAB beginners here:

http://www.mathworks.com/matlabcentral/answers/228557-experts-of-matlab-how-did-you-learn-any-advice-for-beginner-intermediate-users

http://www.mathworks.com/help/matlab/matlab_prog/techniques-for-improving-performance.html

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Answer 1

Mike Garrity 2016-2-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/268595-marker-size-based-on-value#answer_210177

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The help for scatterm says:

scatterm(LAT,LON,S,C) displays colored circles at the locations
specified by the vectors LAT and LON (which must be the same size).

So the 3rd argument is your size data and the 4th argument is your color data.

You'll probably need to scale your size data. It wants values which are in "points squared". A point is 1/72 of an inch. So if I want my largest markers to be 1 inch across, I would do something like this:

seamount = load('seamount.mat');
lat = seamount.y;
lon = seamount.x;
zrange = [min(seamount.z), max(seamount.z)];
cdata = seamount.z;
size_data = (cdata-zrange(1)+1) * 72^2 / diff(zrange);
worldmap([-49 -47.5],[-150 -147.5])
scatterm(lat, lon, size_data, cdata,'filled')