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One basic question - combining two conditions
4 messages · Julia Cains, Karl Ove Hufthammer, Peter Dalgaard +1 more
On Tue, 17 Nov 2009 00:26:13 -0800 (PST) Julia Cains
<julia_cains at yahoo.com> wrote:
how do use this "and" operator to combine two conditions. I am sorry as I know for many of you, this is very basic question but I am new to R and trying to learn it as early as possible.
The 'and' operator is called '&' in R. Try ?'&' to display the help page. You might also be interested in ?ifelse and ?"if"
Karl Ove Hufthammer
Julia Cains wrote:
Dear R helpers Suppose I want to use two conditions if (x >= 42) and (x<48) z = 45 else if (x>= 48) and (x<60) z = 14 how do use this "and" operator to combine two conditions. I am sorry as I know for many of you, this is very basic question but I am new to R and trying to learn it as early as possible. Extremely sorry for this stupid question.
Have a look at help(Logic).
O__ ---- Peter Dalgaard ?ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
On 17-Nov-09 08:26:13, Julia Cains wrote:
Dear R helpers Suppose I want to use two conditions if (x >= 42) and (x<48) z = 45 else if (x>= 48) and (x<60) z = 14 how do use this "and" operator to combine two conditions. I am sorry as I know for many of you, this is very basic question but I am new to R and trying to learn it as early as possible. Extremely sorry for this stupid question. Please guide Julia ************************************************
You can do it by using "&" to express "and". But also be careful
how you lay out an "if ... else ...":
if (x >= 42) & (x<48) { z = 45 } else
if (x >= 48) & (x<60) z = 14
See ?"&" [note the quotes] for general information on the logical
operators, and see ?Control for information about if, if .. else,
and so on.
The point about the layout of "if ... else ..." is that the first
line of
if (x >= 42) & (x<48) { z = 45 }
else if (x >= 48) & (x<60) z = 14
is a complete statement, so will be evaluated without looking
any further. Therefore the second line will be interpreted as
a syntax error, since a stand-alone statement cannot begin
with "else" ("else" needs a matching "if" preceding it; but
that has already been swallowed because the first line was
a complete statement). Putting the "else" in the same line
as the "if" means that R knows it is there before executing
the "if".
Ted.
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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
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Date: 17-Nov-09 Time: 09:15:11
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