Format numbers to significant figures nicely in R

Format numbers to significant figures nicely in R

I want to format numbers in my reports to significant digits, but keep trailing significant zeroes and correctly format large numbers

For instance the numbers c(10.00001,12345,1234.5,123.45,1.2345,0.12345) to 3 significant digits should be 10.0, 12300, 1230, 123, 1.23, 0.123 but I get differing results with different methods (and none seem to work universaly.

> numbers<-c(10.00001,12345,1234.5,123.45,1.2345,0.12345)  > for(n in seq(numbers)){  +   print(signif(numbers[n],digits=3))  +   print(format(numbers[n],digits=3))  +   print(formatC(numbers[n], digits=3,format="fg"))  +   print(formatC(numbers[n], digits=3,format="fg", flag="#"))  +   }  [1] 10  [1] "10"  [1] "  10"  [1] "10.0"  [1] 12300  [1] "12345"  [1] "12345"  [1] "12345."  [1] 1230  [1] "1234"  [1] "1234"  [1] "1234."  [1] 123  [1] "123"  [1] " 123"  [1] "123."  [1] 12.3  [1] "12.3"  [1] "12.3"  [1] "12.3"  [1] 1.23  [1] "1.23"  [1] "1.23"  [1] "1.23"  [1] 0.123  [1] "0.123"  [1] "0.123"  [1] "0.123"  

Here, signif and format round the 10.00001 result. formatC with flag="#" correctly does the small numbers but not the large numbers.

Is there a better way ?

Answer by Dirk Eddelbuettel for Format numbers to significant figures nicely in R

Are you aware of prettyNum() and all its options?

Answer by Richard Herron for Format numbers to significant figures nicely in R

A more barebones option is options(), which just does rounding. If you plan on doing this a lot, I suggest checking out Sweave.

> a <- 1.23456789  > options(digits=2)  > a  [1] 1.2  > options(digits=6)  > a  [1] 1.23457  

Answer by PaulHurleyuk for Format numbers to significant figures nicely in R

Sorry I never updated this at the time. None of the statements in my question, or prettynum worked. In the end I used

print(formatC(signif(numbers[n],digits=3), digits=3,format="fg", flag="#"))  

which correctly coped with trailing zero's and big numbers.

Answer by Ben Haley for Format numbers to significant figures nicely in R

If you like scientific notation

> format(2^31-1, scientific = TRUE, digits = 3)  [1] "2.15e+09"  

Answer by hackR for Format numbers to significant figures nicely in R

Paul Hurley's method above worked well for me for both positive and negative numbers. Below is some code which modifies Paul's solution into a function in which the desired significant figures can be specified.

sigfig <- function(vec, n=3){   ### function to round values to N significant digits  # input:   vec       vector of numeric  #          n         integer is the required sigfig    # output:  outvec    vector of numeric rounded to N sigfig    formatC(signif(vec,digits=n), digits=n,format="fg", flag="#")     }      # end of function   sigfig  

to verify it works OK

numbers <- c(50000.01, 1000.001, 10.00001, 12345, 1234.5, 123.45, 1.2345, 0.12345, 0.0000123456, -50000.01, -1000.001,-10.00001, -12345, -1234.5, -123.45, -1.2345, -0.12345, -0.0000123456)  sigfig(numbers)   # defaults to 3  sigfig(numbers, 3)  sigfig(numbers, 1)  sigfig(numbers, 6)  

Answer by JMT_2080AD for Format numbers to significant figures nicely in R

Another modification on Paul's answer. It appears that it also leaves a trailing decimal. I am removing it with gsub:

sigfig <- function(vec, digits){    return(gsub("\\.$", "", formatC(signif(vec,digits=digits), digits=digits, format="fg", flag="#")))  }  

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