Hi,
Actually, you don't need to create the column first, nor to use which:
DF[DF$month==1, "product1_1"] = DF[DF$month==1, "product1"] * 3.1
The "[" is a great tool that you need to learn. In this case, you don't
need to combine "[" and $: within the square brackets, the vector before
the comma indexes the rows and the one after the comma indexes the columns.
The other thing you were missing correctly referencing the rows. You
have to specify the data.frame you want to look into.
And last, learn to use dput() to provide a nice reproducible example.
HTH,
Ivan
--
Dr. Ivan Calandra
TraCEr, Laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
56567 Neuwied, Germany
+49 (0) 2631 9772-243
https://www.researchgate.net/profile/Ivan_Calandra
On 23/05/2017 08:45, William Michels via R-help wrote:
Hi Lily,
You're on the right track, but you should define a new column first
(filled with NA values), then specify the precise rows and columns on
both the left and right hand sides of the assignment operator that
will be altered. Luckily, this is pretty easy...just remember to use
which() on the right hand side of the assignment operator to get the
index of the rows you want. Example below for "product1":
DF$product1_1 <- NA
DF[DF$month == 1, "product1_1"] <- DF[which(DF$month == 1), "product1"]*3.1
HTH,
Bill.
William Michels, Ph.D.
On Mon, May 22, 2017 at 9:56 PM, lily li <chocol...@gmail.com> wrote:
Hi R users,
I have a question about manipulating the dataframe. I want to create a new
dataframe, and to multiply rows with different seasons for different
constants.
DF
year month day product1 product2 product3
1981 1 1 18 56 20
1981 1 2 19 45 22
1981 1 3 16 48 28
1981 1 4 19 50 21
1981 2 1 17 49 25
1981 2 2 20 47 23
1981 2 3 21 52 27
For example, how to multiply product1 in month1 by 3.1, and to multiply
product3 in month2 by 2.0? I wrote the code like this but does not work.
Thanks for your help.
DF['month'==1, ]$product1_1 = DF['month'==1, ]$product1 * 3.1;
DF['month'==2, ]$product3_1 = DF['month'==1, ]$product3 * 2.0;
[[alternative HTML version deleted]]
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