mauede at alice.it
2009-Mar-30 10:07 UTC
[R] what is R equivalent of Fortran DOUBLE PRECISION ?
I noticed taht R cannot understand certain Fortran real constant formats. For instance: c14 <- as.double( 7.785205408500864D-02) Error: unexpected symbol in " c14 <- as.double( 7.785205408500864D" The above "D" is used in Fortran language to indicate the memory starage mode. That is for instructing Fortran compiler to store such a REAL constant in DOUBLE PRECISION... am I right ? Since R cannot undestand numerical conatant post-fixed by the letter "D", I wonder how I can instruct R interpreter to store such a numerical constant reserving as muh memory as necessary so as to accommodate a double precision number. I noticed R accepts the folllowing syntax but I do not know if i have achieved my goal thsi way:> c14 <- as.double( 7.785205408500864E-02) > typeof(c4)[1] "double" My questions are: what is the best precision I can get with R when dealing with real number ? Is R "double" type equvalent to Fortran DOUBLE PRECISION for internal number representation ? Thank you very much. Maura tutti i telefonini TIM! [[alternative HTML version deleted]]
Steven McKinney
2009-Mar-31 02:45 UTC
[R] what is R equivalent of Fortran DOUBLE PRECISION ?
>From the help page for "Foreign" > ?ForeignNumeric vectors in R will be passed as type double * to C (and as double precision to Fortran) Also, see the help page for "double"> ?doubleR has no single precision data type. All real numbers are stored in double precision format. The functions as.single and single are identical to as.double and double except they set the attribute Csingle that is used in the .C and .Fortran interface, and they are intended only to be used in that context. HTH Steven McKinney, Ph.D. Statistician Molecular Oncology and Breast Cancer Program British Columbia Cancer Research Centre email: smckinney +at+ bccrc +dot+ ca tel: 604-675-8000 x7561 BCCRC Molecular Oncology 675 West 10th Ave, Floor 4 Vancouver B.C. V5Z 1L3 Canada -----Original Message----- From: r-help-bounces at r-project.org on behalf of mauede at alice.it Sent: Mon 3/30/2009 3:07 AM To: r-help at r-project.org Cc: John C. Nash Subject: [R] what is R equivalent of Fortran DOUBLE PRECISION ? I noticed taht R cannot understand certain Fortran real constant formats. For instance: c14 <- as.double( 7.785205408500864D-02) Error: unexpected symbol in " c14 <- as.double( 7.785205408500864D" The above "D" is used in Fortran language to indicate the memory starage mode. That is for instructing Fortran compiler to store such a REAL constant in DOUBLE PRECISION... am I right ? Since R cannot undestand numerical conatant post-fixed by the letter "D", I wonder how I can instruct R interpreter to store such a numerical constant reserving as muh memory as necessary so as to accommodate a double precision number. I noticed R accepts the folllowing syntax but I do not know if i have achieved my goal thsi way:> c14 <- as.double( 7.785205408500864E-02) > typeof(c4)[1] "double" My questions are: what is the best precision I can get with R when dealing with real number ? Is R "double" type equvalent to Fortran DOUBLE PRECISION for internal number representation ? Thank you very much. Maura tutti i telefonini TIM! [[alternative HTML version deleted]] ______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.