[R] Dataframes: conditional calculations per row .

[jim holtman]

You can use 'ifelse':

> x <- data.frame(id=sample(1:4,20,TRUE))
> # use ifelse to do the calculations
> x$cal <- ifelse(x$id == 1, 21,
+            ifelse(x$id == 2, 221,
+               ifelse(x$id == 3, 2221, 22221)))
> x
   id   cal
1   4 22221
2   1    21
3   3  2221
4   1    21
5   2   221
6   2   221
7   1    21
8   2   221
9   4 22221
10  2   221
11  2   221
12  3  2221
13  2   221
14  1    21
15  4 22221
16  3  2221
17  4 22221
18  1    21
19  3  2221
20  2   221


On Mon, Feb 9, 2009 at 5:11 PM, Jesús Guillermo Andrade
<jgandradev at mac.com> wrote:
> Dear Sirs: I've been working with several variables in a dataframe
> that serve as part of a calculation that I need to perform in a
> different way depending on its value. Let me explain:
>
> The main dataframe is called llmcc
>
> llmcc : 'data.frame':   283 obs. of  11 variables:
>  $ Area     : num  308.8 105.6 51.4 51.4 52.9 ...
>  $ mFondo   : num  30.1 10 10.2 10.2 40.4 ...
>  $ mFachada : num  22.95 6.7 4.72 4.72 4.72 ...
>  $ Marca    : Factor w/ 132 levels "AA_Movilnet",..: 11 32 82 82 32
> 32 32 32 32 32 ...
>  $ Clase    : int  8 4 1 1 1 1 1 1 12 1 ...
>  $ Categoria: int  2 6 6 6 1 1 1 1 1 1 ...
>  $ Phi      : num  0.128 0.147 0.217 0.217 0.887 ...
>  $ Rf       : num  0.119 0.102 0.147 0.147 0.143 ...
>  $ OldA     : num  0.737 0.258 0.375 0.375 0.385 ...
>  $ OldCondo : num  4436 1555 2260 2260 2318 ...
>  $ NewA_Jon : num  1.069 0.368 0.256 0.256 0.264 ...
>
> I perform an initial operation using the original variables plus one
> numeric (Abase) that is external and has the same number of rows than
> the dataframe:
>
> alitemp  <- ((Abase/llmcc$Clase)*PClase)+(((1/llmcc
> $Categoria)*Abase)*PCategoria)+((Abase*llmcc$Phi)*PPhi)+((Abase*llmcc
> $Rf)*PRf)
>
> So, after I obtain the results of this calculation, I append the
> series by creating an additional column within the original dataframe:
> l
> lmcc$Alitmp  <- alitemp
>
> Problem is: I need to calculate a new column using a formula that has
> different structure depending on the values of llmcc$Clase, thus: for
> any given row of llmcc where llmcc$Clase is >= 10 i would have to
> perform some operations with other values in the same row that are, by
> definition, different than the ones I would need in case of lmcc$Clase
> is < 10.
> I've managed to break down the original dataframe by using subsets,
> and then performing the calculations, but then it is complicated to
> put the results in the same order of the original dataframe.
> I understand the workings of the control structures available in R but
> after reading the docs and help files, I can´t figure how to perform a
> conditional calculation row by row that checks first the values of a
> given column and then applies the corresponding operation to another
> column, so it outputs a series in the same exact order as the dataframe.
>
> Any light that you might share with me over this will be highly
> appreciated.
>
> Thanks in advance.
>
>
> Guillermo.
>
>
>
> Nunca le preguntes a un peluquero si necesitas un corte de pelo. Ley
> de Murray.
> ------------------------------
> Jesús Guillermo Andrade (Abg.)
> Gerente de Litigios y Corporativo. EDM. AC. API.
> Andrade & Moreno S.C. (http://amlegal.wordpress.com/)
>
>
>        [[alternative HTML version deleted]]
>
>
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>
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?