I want to generate a scatter graph using matlibplot.pyplot and a lot of points are duplicate. So when I simply draw a graph use pyplot.scatter method, many points are overdrawn on one dot. In order to consider the number of points on that position, I think I need to set a different point size, like a bigger circle if the spot contains more data points.
Can someone give me a pointer on how to do this? Thanks!
The easiest way to do this is to set a low alpha, and then when the points plot on top of each other they look darker.
import numpy as np
import matplotlib.pyplot as plt
data = [i for i in range(8) for j in range(np.random.randint(10))]
x, y = np.array(data), np.array(data)
plt.scatter(x, y, alpha=.1, s=400)
plt.show()
Of course, you can also change the size of the point or the color directly. To do this, you need to find the number of overlapping points and then set the size (using the s scatter plot parameter) or the color (using c) or both. (But setting alpha is easiest since it doesn't require explicitly counting the overlaps.)
Related
I am trying to plot the solution curve from this page:
dynamicalsystem
But, I can't draw the arrow in the curve pointing to the origin, and the curve is not spiraling as well. Is something wrong with my code?
using MTH229, ForwardDiff, Plots, LaTeXStrings, SymPy
gr()
t = range(0, stop=21, length=10000)
x = #. exp(-2t)*cos(t)
y = #. exp(-2t)*sin(t)
plot(x, y, arrow = :closed, label=L"x(t)",
xlims=(-0.1,1), ylims=(-0.1,0.21))
You do not see a spiral, because the plot you have linked is not accurate (i.e. it has a wrong scale - most likely for didactic purposes). You can see that you have a spiral, by e.g. plotting the angle of the point plot(t, angle.(x + im * y)). The problem is that the plot absolute value of the points you plot gets very small very fast so these spirals are not visible.
Now the other issue is how to plot the arrow. The arrow in your case is just not visible because it is plotted at the end of your curve. I think (but maybe there are better ways to do it) that the simplest solution to pick a place to add it separately. For example after doing an initial plot add plot!(x[240:241], y[240:241], arrow=:closed) will add an extra arrow in the segment of your curve and the arrow will be visible (you just need to decide on the color of the arrow).
I am trying to plot individual data points on a line plot I already made as follows:
p=plot('3.29*exp(-17.4*(x^2))-0.908',xrange=[0.,1.],yrange=[-1.,1.5])
I first tried overplotting a point like this but nothing appears on the graph
estimate1=plot([0.549],[0.755],overplot=1)
When I give the plot function two points to overplot by adding another set of x and y values in input vectors, it connects them.
estimate=plot([0.349,0.9595],[0.555,0.9995],overplot=1)
How can I (over)plot the points without them being connected?
You should be able to set linestyle = 6 which will plot without the line.
I found a way around the problem I was having. After choosing a symbol for the points I wanted to show, I simply set the transparency of the line connecting them to 100 and the symbol transparency to 0.
estimate1.symbol='diamond'
estimate1.transparency=100
estimate1.sym_transparency=0
The work around is not elegant, but it works.
I am attempting to project data onto a plot in R and see the correlation between the points. I have added a line to let the reader see the connection between these points. I am however stumped when it comes to inputting arrows to show the direction of the line. Rddproj was just an arbitrary name given to the data. Three sets of x and y coordinates are plotted x=c(-0.7159425, -0.8129311, -0.7392371); y=0.7743088, 0.7732762, 0.7490996) Here is the example below.
x<-rddproj[1:3,1]; y<-rddproj[1:3,2]
plot(x,y)
My concern is that the second group of coordinates is the greatest negative point on the x-axis. In drawing a line with arrows, the arrow will most likely point towards this point, when it should be forming a V with that point in the middle. Is it possible to plot an arrow to reflect the placement of points in a group and not just the most positive point to the most negative point or vice versa?
The arrows function ( a modified segments function) is used for this purpose (to the extent that I understand the question) in base R:
# fixed your assignment code.
plot(NA, xlim=range(x), ylim=range(y) )
arrows(head(x,-1),head(y,-1),tail(x,-1), tail(y,-1), angle=30)
An alternative reading of your question would have the glaringly obvious solution : plot(x,y) which I hope is not what you were asking since that should have been satisfactory.
I'm using pyqtgraph for a live view of a camera acquisition program. Most of the times my images are composed of a lot of background noise and a signal of just a few pixels with higher intensity. For that reason, the part of the HistogramLUTItem that corresponds to the actual signal looks like a thin line and the noise is big next to it. Being able to plot the logarithm of the data would make the data to stand up more.
Is this possible?
I'm currently creating the histogram this way:
imagewidget = pg.GraphicsLayoutWidget()
self.p1 = imagewidget.addPlot()
self.img = pg.ImageItem()
self.p1.addItem(self.img)
self.p1.getViewBox().setAspectLocked(True)
self.hist = pg.HistogramLUTItem()
self.hist.setImageItem(self.img)
self.hist.autoHistogramRange = False
imagewidget.addItem(self.hist)
Doing self.hist.axis.setLogMode(True) didn't work as it affected the x-axis of the histogram instead of the y-axis.
And finally, I would also like to be able to limit the accesible range in the x-axis of the histogram. How can this be done?
Cheers!
Ok, I finally figured out. In case someone wonders, I solved it by adding these two lines:
self.hist.plot.setLogMode(False, True)
self.hist.vb.setLimits(yMin=0, yMax=16000)
I want to plot several lists of points, each list has distance (decimal) and error_no (1-8). So far I am using the following:
plot(b1$dist1, b1$e1, col="blue",type="p", pch=20, cex=.5)
points(b1$dist2, b1$e2, col="blue", pch=22)
to add them both to the same plot. (I will add legends, etc later on).
The problem I have is that points overlap, and even when changing the character using for plotting, it covers up previous points. Since I am planning on plotting a lot more than just 2 this will be a big problem.
I found some ways in:
http://www.rensenieuwenhuis.nl/r-sessions-13-overlapping-data-points/
But I would rather do something that would space the points along the y axis, one way would be to add .1, then .2, and so on, but I was wondering if there was any package to do that for me.
Cheers
M
ps: if I missed something, please let me know.
As noted in the very first point in the link you posted, jitter will slightly move all your points. If you just want to move the points on the y-axis:
plot(b1$dist1, b1$e1, col="blue",type="p", pch=20, cex=.5)
points(b1$dist2, jitter(b1$e2), col="blue", pch=22)
Depends a lot on what information you wish to impart to the reader of your chart. A common solution is to use the transparency quality of R's color specification. Instead of calling a color "blue" for example, set the color to #0000FF44 (Apologies if I just set it to red or green) The final two bytes define the transparency, from 00 to FF, so overlapping data points will appear darker than standalone points.
Look at the spread.labs function in the TeachingDemos package, particularly the example. It may be that you can use that function to create your plot (the examples deal with labels, but could just as easily be applied to the points themselves). The key is that you will need to find the new locations based on the combined data, then plot. If the function as is does not do what you want, you could still look at the code and use the ideas to spread out your points.
Another approach would be to restructure your data and use the ggplot2 package with "dodging". Other approaches rather than using points several times would be the matplot function, using the col argument to plot with a vector, or lattice or ggplot2 plots. You will probably need to restructure the data for any of these.