问题
Suppose that (x(t),y(t)) has polar coordinates(√t,2πt). Plot (x(t),y(t)) for t∈[0,10].
There is no proper function in R to plot with polar coordinates. I tried normal plot by giving, x=√t & y=2πt. But resultant graph was not as expected.
I got this question from "Introduction to Scientific Programming and Simulation using r"and the book is telling the plot should be spiral.
回答1:
Make a sequence:
t <- seq(0,10, len=100) # the parametric index
# Then convert ( sqrt(t), 2*pi*t ) to rectilinear coordinates
x = sqrt(t)* cos(2*pi*t)
y = sqrt(t)* sin(2*pi*t)
png("plot1.png");plot(x,y);dev.off()
That doesn't display the sequential character, so add lines to connect adjacent points in the sequence:
png("plot2.png");plot(x,y, type="b");dev.off()
回答2:
As already mentioned in a previous comment, R can plot using polar coordinates. The package plotrix has a function called polar.plot that does this. Polar coordinates are defined by length and angle. This function can take a sequence of lengths and a sequence of angles to plot with polar coordinates. For example to make one spiral:
library(plotrix)
plt.lns <- seq(1, 100, length=500)
angles <- seq(0, 5*360, length=500)%%360
polar.plot(plt.lns, polar.pos=angles, labels="", rp.type = "polygon")
回答3:
An option worth a try, It is Plotly package.
library(plotly)
p <- plot_ly(plotly::mic, r = ~r, t = ~t, color = ~nms, alpha = 0.5, type = "scatter")
layout(p, title = "Mic Patterns", orientation = -90)
Note: If you are using RStudio, the plots are going to be shown in Viewer tab.
来源：https://stackoverflow.com/questions/29193499/how-to-plot-polar-coordinates-in-r