a%%b = 1 but a%%b==1 is FALSE, a and b have limit decimal places

Asked Mar 12 '20 at 01:22

Active Mar 12 '20 at 01:22

Viewed 19 times

info <- rep(NA,20)
for (j in 1:20) {
  info[j] <- pnorm(0.1*j-1,0,1/4.5)-pnorm(0.1*j-1-0.1,0,1/4.5)
}

info <- as.numeric(sprintf("%.5f",info))

initialsol <- as.vector(t(as.matrix(cbind(matrix(0.000001,20,10),as.matrix(info-0.000001*10)))))

In short, initialsol is a vector that sums up to 1 with limit decimal places.

rep(1,220)%*%initialsol

turns out to be 1. However,

rep(1,220)%*%initialsol==1

is FALSE. Why is that?

asked Mar 12 '20 at 01:22

Chp

A simpler version, (rep(1,20)%*%rep(1/20,20))>1 is TRUE while (rep(1,10)%*%rep(1/10,10))>1 is FALSE. – Chp Mar 12 '20 at 01:46
2

That is mostly because of floating-point rounding error. Read https://stackoverflow.com/questions/9508518/why-are-these-numbers-not-equal – Ronak Shah Mar 12 '20 at 01:50
1

Check out `print(rep(1,220)%*%initialsol, digits=20)` for example. – MrFlick Mar 12 '20 at 01:51
It's basic but I didn't know that. Thank you guys! – Chp Mar 12 '20 at 01:55

a%*%b = 1 but a%*%b==1 is FALSE, a and b have limit decimal places

0 Answers0

a%%b = 1 but a%%b==1 is FALSE, a and b have limit decimal places