Here is a test of the different proposed solutions and a new one faster.
In conclusion, ifelse much be used with caution:
Aini = runif(1000000, min=-1,max=1)
library(microbenchmark)
A <- Aini
microbenchmark({B1 <- ifelse( A < 0, sqrt(-A), A )})
# mean = 77.55551
A <- Aini
microbenchmark({B2 <- ifelse( A < 0, suppressWarnings(sqrt(-A)), A )})
# mean = 76.53762
A <- Aini
microbenchmark({B3 <- ifelse( A < 0, sqrt(abs(A)), A )})
# mean = 75.26712
A <- Aini
microbenchmark({A[A < 0] <- sqrt(-A[A < 0]);B4 <- A})
# mean = 17.71883
Marc
Le 09/12/2019 à 19:25, Richard M. Heiberger a écrit :
or even simpler
sqrt(abs(A))
On Mon, Dec 9, 2019 at 8:45 AM Eric Berger <ericjber...@gmail.com> wrote:
Hi Bob,
You wrote "the following error message" -
when in fact it is a Warning and not an error message. I think your
code does what you hoped it would do, in the sense it successfully
calculates the sqrt(abs(negativeNumber)), where appropriate.
If you want to run the code without seeing this warning message you can run
ifelse( A < 0, suppressWarnings(sqrt(-A)), A )
and you should be fine.
HTH,
Eric
On Mon, Dec 9, 2019 at 3:18 PM Kevin Thorpe <kevin.tho...@utoronto.ca> wrote:
The sqrt(-A) is evaluated for all A. The result returned is conditional on the
first argument but the other two arguments are evaluated on the entire vector.
Kevin
--
Kevin E. Thorpe
Head of Biostatistics, Applied Health Research Centre (AHRC)
Li Ka Shing Knowledge Institute of St. Michael's
Assistant Professor, Dalla Lana School of Public Health
University of Toronto
email: kevin.tho...@utoronto.ca Tel: 416.864.5776 Fax: 416.864.3016
On 2019-12-09, 7:58 AM, "R-help on behalf of rsherry8"
<r-help-boun...@r-project.org on behalf of rsher...@comcast.net> wrote:
Please consider the following two R statements:
A = runif(20, min=-1,max=1)
ifelse( A < 0, sqrt(-A), A )
The second statement produces the following error message:
rt(-A) : NaNs produced
I understand that you cannot take the square root of a negative number
but I thought the condition A < 0
would take care of that issue. It appears not to be.
What am I missing?
Thanks,
Bob
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