[R] Can't compute row means of two columns of a dataframe.

[Ebert,Timothy Aaron]

Can this problem be made more direct?

xxxz$Average.20 <- (xxxz$Low20 + xxxz$High20)/2

That is literally the mean of two columns. Functions can be useful if there will be more columns, but with just two this seems easier.

I will point out that the average daily temperature based on the midpoint between minimum and maximum contains a fair bit of error because that is only roughly how heating and cooling respond. I admit that sometimes there are no other choices and we work with available data.

Tim


-----Original Message-----
From: R-help <r-help-bounces using r-project.org> On Behalf Of Sorkin, John
Sent: Saturday, June 8, 2024 1:38 PM
To: r-help using r-project.org (r-help using r-project.org) <r-help using r-project.org>
Subject: [R] Can't compute row means of two columns of a dataframe.

[External Email]

I have a data frame with three columns, TotalInches, Low20, High20. For each row of the dataset, I am trying to compute the mean of Low20 and High20.

xxxz <- structure(list(TotalInches =
                 c(58, 59, 60, 61, 62, 63, 64, 65,
                   66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76), Low20 = c(84, 87,
                   90, 93, 96, 99, 102, 106, 109, 112, 116, 119, 122, 126, 129,
                   133, 137, 141, 144), High20 = c(111, 115, 119, 123, 127, 131,
                   135, 140, 144, 148, 153, 157, 162, 167, 171, 176, 181, 186, 191
                   )), class = "data.frame", row.names = c(NA, -19L)) xxxz
str(xxxz)
xxxz$Average20 <- by(xxxz[,c("Low20","High20")],xxxz[,"TotalInches"],mean)
warnings()

When I run the code above, I don't get the means by row. I get the following warning messages, one for each row of the dataframe.

Warning messages:
1: In mean.default(data[x, , drop = FALSE], ...) :
  argument is not numeric or logical: returning NA
2: In mean.default(data[x, , drop = FALSE], ...) :
  argument is not numeric or logical: returning NA

 Can someone tell my what I am doing wrong, and how I can compute the row means?

Thank you,
John

John David Sorkin M.D., Ph.D.
Professor of Medicine, University of Maryland School of Medicine; Associate Director for Biostatistics and Informatics, Baltimore VA Medical Center Geriatrics Research, Education, and Clinical Center; PI Biostatistics and Informatics Core, University of Maryland School of Medicine Claude D. Pepper Older Americans Independence Center; Senior Statistician University of Maryland Center for Vascular Research;

Division of Gerontology and Paliative Care,
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
Cell phone 443-418-5382



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