... Perhaps worth adding is the use of poly() rather than separately created terms for (non/orthogonal) polynomials:
lm(y ~ poly(x, degree =2) #orthogonal polyomial of degree 2 see ?poly for details. -- Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Tue, Dec 18, 2018 at 6:14 PM rsherry8 <rsher...@comcast.net> wrote: > Richard, > > It is now working. > > Thank you very much. > > Bob > On 12/18/2018 7:10 PM, Richard M. Heiberger wrote: > > ## This example, with your variable names, works correctly. > > > > z2 <- data.frame(y=1:5, x=c(1,5,2,3,5), x2=c(1,5,2,3,5)^2) > > z2 > > class(z2) > > length(z2) > > dim(z2) > > > > lm(y ~ x + x2, data=z2) > > > > ## note that that variable names y, x, x2 are column names of the > > ## data.frame z2 > > > > ## please review the definitions and examples of data.frame in > ?data.frame > > ## also the argument requirements for lm in ?lm > > > > On Tue, Dec 18, 2018 at 6:32 PM rsherry8 <rsher...@comcast.net> wrote: > >> The values read into z2 came from a CSV file. Please consider this R > >> session: > >> > >> > length(x2) > >> [1] 1632 > >> > length(x) > >> [1] 1632 > >> > length(z2) > >> [1] 1632 > >> > head(z2) > >> [1] 28914.0 28960.5 28994.5 29083.0 29083.0 29083.0 > >> > tail(z2) > >> [1] 32729.65 32751.85 32386.05 32379.75 32379.15 31977.15 > >> > lm ( y ~ x2 + x, z2 ) > >> Error in eval(predvars, data, env) : > >> numeric 'envir' arg not of length one > >> > lm ( y ~ x2 + x, as.data.frme(z2) ) > >> Error in as.data.frme(z2) : could not find function "as.data.frme" > >> > lm ( y ~ x2 + x, as.data.frame(z2) ) > >> Error in eval(predvars, data, env) : > >> numeric 'envir' arg not of length one > >> lm(formula = y ~ x2 + x, data = as.data.frame(z2)) > >> > >> Coefficients: > >> (Intercept) x2 x > >> -1.475e-09 1.000e+00 6.044e-13 > >> > >> > min(z2) > >> [1] 24420 > >> > max(z2) > >> [1] 35524.85 > >> > class(z2) > >> [1] "numeric" > >> > > >> > >> where x is set to x = seq(1:1632) > >> and x2 is set to x^2 > >> > >> I am looking for an interpolating polynomial of the form: > >> Ax^2 + Bx + C > >> I do not think the results I got make sense. I believe that I have a > >> data type error. I do not understand why > >> I need to convert z2 to a data frame if it is already numeric. > >> > >> Thanks, > >> Bob > >> > >> ______________________________________________ > >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > >> 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. > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
