R help - Apr 2008 - Replace values according to conditions

Greetings R-users,

I have the following data called mydata in a data.frame

Col1 Col2 Col3 Col4 Col5
1       2     4    6      7
8       8     7    3      5
4      4      5    6      7

I want to replace the data according to the following conditions

Condition 1   if data <= 3, replace with -1
Condition 2   if data >=6, replace with 1
Condition 3    if data = 4 or data =5, replace with 0

So the expected output for the example, would be
Col1 Col2 Col3 Col4 Col5
-1      -1     0   1      1
1       1     1   -1     0
0       0     1    1     1

I have thought of using replace with each conditions, for example I tried
the following

myrep <- replace(mydata, mydat <= 3, -1 )   #Condition 1

I would have to repeat the function replace for each of the conditions to
get the expected output.

My questions are:

1. I would like to know if there are better ways to achieve the expected
output?
2. What are the symbols for OR and AND in R?

Thanks for any feedback


-- 
Suhaila Zainudin

	[[alternative HTML version deleted]]

> I have the following data called mydata in a data.frame
> 
> Col1 Col2 Col3 Col4 Col5
> 1       2     4    6      7
> 8       8     7    3      5
> 4      4      5    6      7
> 
> I want to replace the data according to the following conditions
> 
> Condition 1   if data <= 3, replace with -1
> Condition 2   if data >=6, replace with 1
> Condition 3    if data = 4 or data =5, replace with 0
> 
> So the expected output for the example, would be
> Col1 Col2 Col3 Col4 Col5
> -1      -1     0   1      1
> 1       1     1   -1     0
> 0       0     1    1     1
>...
> 1. I would like to know if there are better ways to achieve the expected
> output?
mydata[mydata<=3] = -1
mydata[mydata==4 | mydata==5] = 0
mydata[mydata>=6] = 1

See the Intro to R, section 2.7.
> 2. What are the symbols for OR and AND in R?
There are two versions: | and & that do elementwise logical comparisons on 
vectors; and || and && that are quicker for scalar logical comparisons 
(mostly used in 'if' statement conditions).

See the Intro to R, section 2.4 and 9.2.1.

Regards,
Richie.

Mathematical Sciences Unit
HSL


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