I have several thousands of points to plot (about 10k) and I would like to plot them with Matlab but deciding a diferent size for each of the points (and a different color if possible). I tried to make a scatter plot for each point, but it is extremely slow compared to a single scatter call for all the points. Is there a way to plot several points in Matlab with different properties for each point, that works in a reasonable amount of time?
In case it is not possible to do it with Matlab, is there a way to do it with gnuplot?
scatter(x, y, a, c) takes arguments x and y, and then a for size, and c for colour. a can either be a single scalar, or a vector with a size for each (x,y) point. c can be an RGB triplet, or a vector, the same size as x and y. For example:
x = 1:4;
scatter(x, x, 10*x, x);
results in
So in your case, perhaps
scatter(xData, yData, [], 1:10000)
will result in your data having a different colour determined by its position in the data array.
For gnuplot it's easy, suppose you write your datafile with 3 columns, all you have to do is
plot 'data.dat' u 1:2:3:3 with circles lc palette
HERE you can find some examples (for help type help circles).
If you want just what is called variable pointsize (pointsize is not related to the real axis) you can use:
plot 'data.dat' with points ps variable pt 7
HERE you can find some examples (for help type help pointsize).
For gnuplot you can combine pointsize variable and linecolor variable or linecolor palette:
set xrange [0:10]
set samples 21
plot '+' using 1:1:(0.2*$1):1 with point pointsize variable linecolor palette pt 7 notitle
Related
I want to plot a text file with 4 columns that first column in longitude,second in latitude, third is depth and forth is amount of displacement in each point.(it's related to a fualt)
-114.903874 41.207504 1.446784 2.323745
I want a plot to show the amount of displacement in each point (like images that we plot with imagesc),unfortunately "imagesc" command doesn't work for it.
how can I plot it?
Thanks for your attention
A simple way would be to use scatter3 and assign your displacements to be the colours. Note that you have to supply a size for this to work - I'm using [] (empty matrix) which will set it to default. If your four sets of values are four vectors of the same size, then it's just something like:
scatter3(lat,lon,depth,[],displacement, 'filled')
Values in displacement will be linearly mapped to the current colormap. 'filled' gives you filled markers rather than open ones (default marker is a circle but can be changed).
You can plot each point using plot3(longitude,latitude,depth). You can color each point according to the displacement in a for loop. The easiest way to do this is create a colormap, e.g. using jet and chosing the color according to the displacement.
figure;
hold on;
cmap = jet(256);
dispRange = [min(displacement),max(displacement)];
for k=1:size(longitude,2)
c = cmap(1+round(size(cmap,1)*(displacement(k)-dispRange(1))/dispRange(2)),:);
plot3(longitude(k),latitude(k),depth(k),'o', ...
'MarkerEdgeColor',c,'MarkerFaceColor',c);
end
I need to plot a 3D figure with each data point colored with the value of a 4th variable using a colormap. Lets say I have 4 variables X,Y,Z and W where W = f(X,Y,Z). I want a 3D plot with X, Y, and Z as the three axis. The statement scatter3(X,Y,Z,'filled','b') gives me a scatter plot in 3D but I want to incorporate the value of Z in the graph by representing the points as an extra parameter (either with different areas :bigger circles for data points with high value of Z and small circles for data points with low value of Z or by plotting the data points with different colors using a colormap). However, I am a novice in MATLAB and dont really know how to proceed. Any help will be highly appreciated.
Thanks in advance!
So just use z for the size vector (4th input) as well as the color vector (5th input):
z = 10*(1:pi/50:10*pi);
y = z.*sin(z/10);
x = z.*cos(z/10);
figure(1)
scatter3(x,y,z,z,z)
view(45,10)
colorbar
The size vector needs to be greater 0, so you may need to adjust your z accordingly.
You are already nearly there... simply use
scatter3(X,Y,Z,s,W);
where s is the point size (scalar, e.g. 3) and W is a vector with your W values.
You might also want to issue an
set(gcf, 'Renderer','OpenGL');
where gcf gets your current figure you are plotting in to significantly increase responsiveness when scattering a lot of data.
I am trying to make a simple plot (for this example doing a plot of y=x^2 will suffice) where I want to set the colors of the points based on their magnitude given some colormap.
Following along my simple example say I had:
x = 1:10;
y = x.^2;
Use gscatter(x,y,jet(10)); legend hide; colorbar which produces a plot with the points colored but the colorbar does not agree with the colored values. (Can't post picture as this is my first post). Using a caxis([1,100]) command gives the right range but the colors are still off.
So I have two questions:
(1) How can I fix the colors to fit to a colorbar given a range? In my real data, I am looking at values that range from -50 to 50 in some instances and have many more data points.
(2) I want to create a different plot with the same points (but on different axes) and I want the colors of each point on this new plot to have the same colors as their counterparts in the previous plot. How can I, programmatically, extract the color from each point so I can plot it on two different sets of axes?
I would just move the points into a matrix and do an imagesc() command but they aren't spaced as integers or equally so simple scaling wouldn't work either.
Thanks for any help!
Regarding you first question, you need to interpolate the y values into a linear index to the colormap. Something like:
x = 1:10;
y = x.^4;
csize = 128;
cmap = jet(csize);
ind = interp1(linspace(min(y),max(y),csize),1:csize,y,'nearest');
scatter(x,y,14,cmap(ind,:),'filled')
colorbar
caxis([min(y) max(y)])
Using interp1 in this case is an overkill; you could calculate it directly. However, I think in this way it is clearer.
I think it also answers your 2nd question, since you have the index of the color of each data point, so you can use it again in the same way.
I have a matrix M, 135*191*121 double and want to plot it in 3D volume by using those 121 slices. How can I do this? (I need a grayscale image)
Regards
Check out vol3d v2 , it an update to Joe Conti's vol3d function, allowing voxel colors and alpha values to be defined explicitly. In cases where voxels can be any RGB color, use:
vol3d('CData', cdata);
where cdata is an MxNxPx3 array, with RGB color along the 4th dimension. In cases where color and alpha values are highly independent, specify an MxNxP alphamatte as follows:
vol3d('CData', cdata, 'Alpha', alpha);
if you have 3 arrays, storing (x,y,z) coordinates of every point that you need to plot, then you can use function plot3
From matlab help
PLOT3 Plot lines and points in 3-D space.
PLOT3() is a three-dimensional analogue of PLOT().
PLOT3(x,y,z), where x, y and z are three vectors of the same length,
plots a line in 3-space through the points whose coordinates are the
elements of x, y and z.
PLOT3(X,Y,Z), where X, Y and Z are three matrices of the same size,
plots several lines obtained from the columns of X, Y and Z.
Various line types, plot symbols and colors may be obtained with
PLOT3(X,Y,Z,s) where s is a 1, 2 or 3 character string made from
the characters listed under the PLOT command.
PLOT3(x1,y1,z1,s1,x2,y2,z2,s2,x3,y3,z3,s3,...) combines the plots
defined by the (x,y,z,s) fourtuples, where the x's, y's and z's are
vectors or matrices and the s's are strings.
Example: A helix:
t = 0:pi/50:10*pi;
plot3(sin(t),cos(t),t);
PLOT3 returns a column vector of handles to lineseries objects, one
handle per line. The X,Y,Z triples, or X,Y,Z,S quads, can be
followed by parameter/value pairs to specify additional
properties of the lines.
for 3d plots you may also want to look into surf function
In a 3D scatter graph of MATLAB I have 15 different clusters of data that I want to highlight. I can see MATLAB has 8 specific colors. Is there any other way I could use 7 more colors just to distinguish the clusters?
Thanks
I would recommend to use this File Exchange submission - Generate maximally perceptually-distinct colors
It allows you to create a colormap with very distinguished colors and apply them with COLORMAP function. See help for this submission for more options.
colors = distinguishable_colors(n_colors);
For 3D scatter you can use this colors as an argument (C) in SCATTER3:
scatter3(X,Y,Z,[],colors)
To use this colors for different lines set them as default color order either for current figure:
set(gcf,'DefaultAxesColorOrder',colors)
or all figures:
set(0,'DefaultAxesColorOrder',colors
You can use the color property using set. You must first get a handle h to the drawing objects and set(h,'color',[0.2 0.3 0.9]). The color is rgb ranging from 0 to 1 for each channel.
From the Matlab documentation:
scatter(X,Y,S,C) displays colored circles at the locations specified
by the vectors X and Y (which must be the same size).
S determines the area of each marker (specified in points^2). S can be
a vector the same length as X and Y or a scalar. If S is a scalar,
MATLAB draws all the markers the same size. If S is empty, the default
size is used.
C determines the color of each marker. When C is a vector the same
length as X and Y, the values in C are linearly mapped to the colors
in the current colormap. When C is a 1-by-3 matrix, it specifies the
colors of the markers as RGB values. If you have 3 points in the
scatter plot and wish to have the colors be indices into the colormap,
C should be a 3-by-1 matrix. C can also be a color string (see
ColorSpec for a list of color string specifiers).
So, for example, say that your clusters are given by the columns of the matrices X and Y, with the k'th column being the k'th cluster, X being the X coordinates, and Y being the Y coordinates. We can do what you want as follows:
% make some random data in clusters:
n = 15;
m = 42;
X = 0.2*rand(m,n) + repmat(rand(1,n),m,1);
Y = 0.2*rand(m,n) + repmat(rand(1,n),m,1);
% lets change the colour map:
colormap(jet);
% now plot each, one at a time, and each with a different colour:
hold on;
for k=1:n
scatter(X(:,k),Y(:,k),40,k/n*ones(m,1));
end
If you don't like these colours, you can change the colormap, and if you don't like the color maps, you can, as the other answer points out, insert any RGB values you want.