R help - Aug 2010 - How to apply apply?!

guRus

I have say a dataframe, d and I wish to do the following:

1) For each row, I want to take one particular value of the row and multiply
it by 2. How do I do it. Say the data frame is as below:
   OPEN HIGH LOW CLOSE 1931.2 1931.2 1931.2 1931.2 0 0 0 999.05 0 0 0 1052.5
0 0 0 987.8 0 0 0 925.6 0 0 0 866 0 0 0 1400.2 0 0 0 754.5 0 0 0 702.6 0 0 0
653.25 0 0 0 348 0 0 0 801 866.55 866.55 866.55 866.55 783.1 783.1 742.25
742.25 575 575 575 575 0 0 0 493 470 470 420 425 355 360 343 360 312.05
312.05 274 280.85 257.35 257.35 197 198.75 182 185.95 137 150.75 120.25 129
90.7 101.25 91.85 91.85 57 66.6

How do I multiply only the close of every row using the 'apply'
function?
And once multiplied how do I obtain a new table that also contains the new
2*CLOSE column (without cbind?).

2) Also, how do I run a generic function per row. Say for example I want to
calculate the Implied Volatility for each row of this data frame ( using the
RMterics package). How do I do that please using the apply function? I am
focusing on apply because I like the vectorisation concept in R and I do not
want to use a for loop etc.

Many thanks for the enlightment,
Raghu

	[[alternative HTML version deleted]]

For 1, an easy way is

dat <- transform(dat, CLOSE2=2*CLOSE)

For 2:

apply(dat,1,fun)

On 08/06/2010 03:06 PM, Raghuraman Ramachandran wrote:
> guRus
>
> I have say a dataframe, d and I wish to do the following:
>
> 1) For each row, I want to take one particular value of the row and
multiply
> it by 2. How do I do it. Say the data frame is as below:
>     OPEN HIGH LOW CLOSE 1931.2 1931.2 1931.2 1931.2 0 0 0 999.05 0 0 0
1052.5
> 0 0 0 987.8 0 0 0 925.6 0 0 0 866 0 0 0 1400.2 0 0 0 754.5 0 0 0 702.6 0 0
0
> 653.25 0 0 0 348 0 0 0 801 866.55 866.55 866.55 866.55 783.1 783.1 742.25
> 742.25 575 575 575 575 0 0 0 493 470 470 420 425 355 360 343 360 312.05
> 312.05 274 280.85 257.35 257.35 197 198.75 182 185.95 137 150.75 120.25 129
> 90.7 101.25 91.85 91.85 57 66.6
>
> How do I multiply only the close of every row using the 'apply'
function?
> And once multiplied how do I obtain a new table that also contains the new
> 2*CLOSE column (without cbind?).
>
> 2) Also, how do I run a generic function per row. Say for example I want to
> calculate the Implied Volatility for each row of this data frame ( using
the
> RMterics package). How do I do that please using the apply function? I am
> focusing on apply because I like the vectorisation concept in R and I do
not
> want to use a for loop etc.
>
> Many thanks for the enlightment,
> Raghu
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>    

-- 

Abhijit Dasgupta, PhD
Director and Principal Statistician
ARAASTAT
Ph: 301.385.3067
E: adasgupta at araastat.com
W: http://www.araastat.com

Raghuraman Ramachandran wrote:
> guRus
> 
> I have say a dataframe, d and I wish to do the following:
> 
> 1) For each row, I want to take one particular value of the row and
multiply
> it by 2. How do I do it. Say the data frame is as below:
>    OPEN HIGH LOW CLOSE 1931.2 1931.2 1931.2 1931.2 0 0 0 999.05 0 0 0
1052.5
> 0 0 0 987.8 0 0 0 925.6 0 0 0 866 0 0 0 1400.2 0 0 0 754.5 0 0 0 702.6 0 0
0
> 653.25 0 0 0 348 0 0 0 801 866.55 866.55 866.55 866.55 783.1 783.1 742.25
> 742.25 575 575 575 575 0 0 0 493 470 470 420 425 355 360 343 360 312.05
> 312.05 274 280.85 257.35 257.35 197 198.75 182 185.95 137 150.75 120.25 129
> 90.7 101.25 91.85 91.85 57 66.6
Much easier to give us the ?dput output so we can construct this!
> 
> How do I multiply only the close of every row using the 'apply'
function?
> And once multiplied how do I obtain a new table that also contains the new
> 2*CLOSE column (without cbind?).
Guessing here... but why do you want to use apply? Isn't

df$new.col <- df$CLOSE * 2

what you want?
> 
> 2) Also, how do I run a generic function per row. Say for example I want to
> calculate the Implied Volatility for each row of this data frame ( using
the
> RMterics package). How do I do that please using the apply function? I am
> focusing on apply because I like the vectorisation concept in R and I do
not
> want to use a for loop etc.
Simply read ?apply to see examples.  Apply works on matrices, not 
data.frames, so if you give it a data.frame, it will be coerced into a 
matrix.

apply(your.data, 1, your.function)

> How do I multiply only the close of every row using the 'apply'
function?
> And once multiplied how do I obtain a new table that also contains the new
> 2*CLOSE column (without cbind?).
You don't use apply in this case - a simple multiplication and
variable assignment will do:
> require(tseries)
> foo <- get.hist.quote('^GDAXI')
> foo[1:10, ]
             Open   High    Low  Close
1991-01-02 1375.4 1375.4 1359.1 1366.1
1991-01-03 1371.7 1374.7 1365.2 1366.7
1991-01-04 1375.4 1398.0 1375.4 1396.1
1991-01-07 1373.6 1373.6 1352.5 1358.2
1991-01-08 1350.4 1357.1 1345.5 1354.0
1991-01-09 1358.6 1380.8 1358.0 1375.2
1991-01-10 1367.9 1383.7 1363.1 1383.4
1991-01-11 1401.3 1406.4 1376.9 1382.3
1991-01-14 1354.5 1354.5 1327.8 1327.8
1991-01-15 1327.0 1330.3 1312.4 1325.6
> foo$Close <- foo$Close * 2
> foo$Close <- foo$Close * 2
> foo[1:10, ]
             Open   High    Low  Close
1991-01-02 1375.4 1375.4 1359.1 2732.2
1991-01-03 1371.7 1374.7 1365.2 2733.4
1991-01-04 1375.4 1398.0 1375.4 2792.2
1991-01-07 1373.6 1373.6 1352.5 2716.4
1991-01-08 1350.4 1357.1 1345.5 2708.0
1991-01-09 1358.6 1380.8 1358.0 2750.4
1991-01-10 1367.9 1383.7 1363.1 2766.8
1991-01-11 1401.3 1406.4 1376.9 2764.6
1991-01-14 1354.5 1354.5 1327.8 2655.6
1991-01-15 1327.0 1330.3 1312.4 2651.2
> 2) Also, how do I run a generic function per row. Say for example I want to
> calculate the Implied Volatility for each row of this data frame ( using
the
> RMterics package). How do I do that please using the apply function? I am
> focusing on apply because I like the vectorisation concept in R and I do
not
> want to use a for loop etc.
You can get the manual page of any R-command by either preceding it
by a question mark or giving the command as an argument to the help
function - specificly:

?apply
help(apply)

Especially the example section is useful for a jumpstart.
Here is an example of computing row means:

apply(foo, 1, mean)

Instead of 'mean' you can insert whatever function you'd like to
apply.

cu
	Philipp

-- 
Dr. Philipp Pagel
Lehrstuhl f?r Genomorientierte Bioinformatik
Technische Universit?t M?nchen
Wissenschaftszentrum Weihenstephan
Maximus-von-Imhof-Forum 3
85354 Freising, Germany
http://webclu.bio.wzw.tum.de/~pagel/