Print values for multiple variables on the same line from within a for-loop

Question

I have a question that must surely seem very trivial, but the answer has always alluded me: how do you print values for multiple variables on the same line from within a for-loop?

I present two solutions neither of which relies on nothing more than a formatted print statement, and I am still interested in whether print can, by itself, be used to return output in the desired format.

First I present the for-loop, which contains one solution, and then I present a function that represents another solution:

P <- 243.51
t <- 31 / 365
n <- 365

for (r in seq(0.15, 0.22, by = 0.01)) {

     A <- P * ((1 + (r/ n))^ (n * t))
     interest <- A - P

     # this prints each variable on a separate line
     print (r)
     print (interest)

     # this does not work
     # print c(r, interest)

     # this presents both variables on the same line, as desired
     output <- c(r,interest)
     print(output)

     # EDIT - I just realized the line below prints output in the desired format
     print (c(r, interest))

}


# this function also returns output in the desired format

data.fn <- function(r) {

     interest <- P*(1+(r/ n))^(n*t) - P
     list(r = r, interest = interest)

}

my.output <- as.data.frame(data.fn(seq(0.15, 0.22, by = 0.01)))
my.output

#      r interest
# 1 0.15 3.121450
# 2 0.16 3.330918
# 3 0.17 3.540558
# 4 0.18 3.750370
# 5 0.19 3.960355
# 6 0.20 4.170512
# 7 0.21 4.380842
# 8 0.22 4.591345

Is there a way to format print statements in the for-loop so that the print statement, by itself, returns output formatted as in my.output? I know that I could also place a matrix inside the for-loop that stores the values of r and interest and then print the matrix after the loop finished. However, I thought using a print statement would be easier, especially since I do not need to retain the values of r or interest.

Thank you for any advice. Sorry again this question is so trivial. I have searched quite a bit for the answer over an extended period, but have never found the solution. Maybe I have presented enough solutions in this post to make additional possible solutions overkill. Nevertheless, I remain interested.

EDIT:

In addition to the helpful responses below I just realized that using:

print (c(r, interest))

in the above for-loop also works.

Have a look at cat instead of print. – Dieter Menne Apr 15 '12 at 08:20 — Dieter Menne, Apr 15 '12 at 08:20

score 25 · Accepted Answer · edited May 23 '17 at 12:17

25

Try out cat and sprintf in your for loop.

eg.

cat(sprintf("\"%f\" \"%f\"\n", df$r, df$interest))

See here

edited May 23 '17 at 12:17

Community

1
1

answered Apr 15 '12 at 08:29

Tejas Patil

6,149
1
23
38

7

it'd much better to do `cat("var1 = ", var1, "var2 = ", var2, "\n")` when you want to inspect var when debugging, or you don't want to care about vars' type – Sang Sep 16 '18 at 09:25

score 4 · Answer 2 · answered Apr 15 '12 at 08:35

As an additional note, there is no need for the for loop because of R's vectorization.

This:

P <- 243.51
t <- 31 / 365
n <- 365

for (r in seq(0.15, 0.22, by = 0.01))    
     A <- P * ((1 + (r/ n))^ (n * t))
     interest <- A - P
}

is equivalent to:

P <- 243.51
t <- 31 / 365
n <- 365
r <- seq(0.15, 0.22, by = 0.01)
A <- P * ((1 + (r/ n))^ (n * t))
interest <- A - P

Because r is a vector, the expression above containing it is performed for all values of the vector.

Print values for multiple variables on the same line from within a for-loop

2 Answers2