I have a function,
x= (z-z^2.5)/(1+2*z-z^2)
y = z-z^2.5
where z
is the only variable. How to draw a graph where x-axis
shows value of function x
, and y-axis
shows value of function y
as z
range from 0 to 5
?
You can get a very basic plot by simply following your own instructions.
## z ranges from 0 to 5
z = seq(0,5,0.01)
## x and y are functions of z
x = (z-z^2.5)/(1+2*z-z^2)
y = z-z^2.5
##plot
plot(x,y, pch=20, cex=0.5)
If you want a smooth curve it is a little trickier. There is a discontinuity in the curve at
z = 1 + sqrt(2) ~ 2.414
. If you just draw the curve as one piece, you get an unwanted line connecting across the discontinuity. So, in two pieces,
plot(x[1:242],y[1:242], type='l', xlab='x', ylab='y',
xlim=range(x), ylim=range(y))
lines(x[243:501],y[243:501])
But be careful about interpreting this. There is something tricky going on from z=0 to z=1.
Using ggplot2
# z ranges from -1000 to 1000 (The range can be arbitrary)
z = seq(-1000,1000,.25)
# x as a function of z
x = (z-z^2.5) / ((1+2*z)-z^2)
# y as a function of z
y = z-z^2.5
# make a dataframe of x,y and z
df <- data.frame(x=x, y=y, z=z)
# subset the df where z is between 0 and 5
df_5 <- subset(df, (df$z>=0 & df$z<=5))
# plot the graph
library(ggplot2)
ggplot(df_5, aes(x,y))+ geom_point(color="red")
The only addition to @G5W answer is subset()
of values between 0
and 5
from your dataset to plot and the use of ggplot2
.
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