情节没有显示CDF

Question

I am trying to plot some cumulative distribution functions for different equations on the same plot, this is the code I have written:

library (triangle)
library(lattice)
library(latticeExtra)
n = 1000

W1 = rtriangle(n,3128,3250)
W2 = rtriangle(n,3065,3149)
SO = rtriangle(n,0.2,0.3)

MCtab <- data.frame(W1,W2,SO)

set.seed(1)
for (n in 1:n) {
NPV30 <- (1*W1 + 2*W2 + 3*SO )}

set.seed(1)
for (n in 1:n) {
NPV50 <- ecdf((4*W1 + 5*W2 + 6*SO ))}  
set.seed(1)
for (n in 1:n) {
NPV70 <- ecdf((7*W1 + 8*W2 + 9*SO))} 

MCtab2 <- data.frame(NPV30,NPV50,NPV70)



plot(NPV30, verticals=TRUE, main= 'Polymer NPV CDF', do.points=FALSE, col='red')
plot(NPV50, verticals=TRUE, do.points=FALSE, add=TRUE, col='brown')
plot(NPV70, verticals=TRUE, do.points=FALSE, add=TRUE, col='orange')

Only one plot is shown cant seem to figure out why, or if someone has a better approach would be great. Thanks

Answer 1

I assuming there is an ecdf missing in front of your NPV30 assignment in the sample code. I think the actual reason it is not displaying the values is that the plot.ecdf method simply does not support the add parameter. But you can roll your own pretty easily.

The values you chose for the functions give such different distributions that the cumulative distribution plot is pretty boring - just rectangles. So I adjusted the defining values for NPV50 and NPV70 to make the three distributions more similar.

So here is the code I used:

library (triangle)
library(lattice)
library(latticeExtra)
n = 50

W1 = rtriangle(n,3128,3250)
W2 = rtriangle(n,3065,3149)
SO = rtriangle(n,0.2,0.3)

MCtab <- data.frame(W1,W2,SO)

set.seed(1)
for (n in 1:n) {
  NPV30 <- ecdf((1*W1 + 2*W2 + 3*SO ))}

set.seed(1)
for (n in 1:n) {
  NPV50 <- ecdf((1*W1 + 2.2*W2 + 3.1*SO ))}  
set.seed(1)
for (n in 1:n) {
  NPV70 <- ecdf((1*W1 + 2.4*W2 + 3.2*SO))} 

MCtab2 <- data.frame(NPV30,NPV50,NPV70)

qNPV30 <- quantile(NPV30)
qNPV50 <- quantile(NPV50)
qNPV70 <- quantile(NPV70)
xmin <- min(c(qNPV30[1],qNPV50[1],qNPV70[1]))
xmax <- max(c(qNPV30[5],qNPV50[5],qNPV70[5]))
xdlt <- xmax-xmin

npts <- 200
x <- (1:npts)*xdlt/npts + xmin
y30 <- NPV30(x)
y50 <- NPV50(x)
y70 <- NPV70(x)

plot(x,y30,main= 'Polymer NPV CDF',xlim=c(xmin,xmax),type='l',col='red')
lines(x,y50,xlim=c(xmin,xmax),type='l',col='blue',add=T)
lines(x,y70,xlim=c(xmin,xmax),type='l',col='green',add=T)

#plot(NPV30, verticals=TRUE, main= 'Polymer NPV CDF', do.points=FALSE, col='red')
#plot(NPV50, verticals=TRUE, do.points=F, add=TRUE, col='blue')
#plot(NPV70, verticals=TRUE, do.points=F, add=TRUE, col='green')

and here is the resulting output: