# [R] Computing growth rate

Brijesh Mishra brijeshkmishra at gmail.com
Thu Dec 15 13:28:23 CET 2016

```Dear Mr. Barradas,

Thanks a lot for pointing that. I tried that in a few steps-
1. when I evaluated

d<-ddply(df1,"co_code1",transform, growth <- ifelse(diff(fyear1)==1,
(exp(diff(log(df1\$sales1)))-1)*100, NA))

I got the following, i.e., I was not getting the growth column automatically.

co_code1 fyear1 sales1
1      1100   1990   1000
2      1100   1991   1100
3      1100   1992   1200
4      1100   1993   1300
5      1100   1995   1500
6      1100   1996   1600
7      1200   1991   1100
8      1200   1992   1200
9      1200   1993   1300
10     1200   1994   1400
11     1200   1995   1500
12     1200   1996   1600
13     1300   1990   1000
14     1300   1992   1200
15     1300   1993   1300
16     1300   1994   1400
17     1300   1995   1500
18     1300   1996   1600

2. When, just for the heck of it, the assign mark (<-) was changed to
'=' as done previously,

d<-ddply(df1,"co_code1",transform, growth = ifelse(diff(fyear1)==1,
(exp(diff(log(df1\$sales1)))-1)*100, NA))

It was no longer evaluated-error was

"Error in data.frame(list(co_code1 = c(1100, 1100, 1100, 1100, 1100, 1100 :
arguments imply differing number of rows: 6, 5"

3. The following gives the desired result

df1\$growth<-c(NA, ifelse(diff(df1\$fyear1)==1,
(exp(diff(log(df1\$sales1)))-1)*100, NA))

But now I am no longer restricting each iteranation to
'co_code1'-hypothetically if one co_code1 is followed by another with
incremental 'fyear1' difference as 1, growth will be evaluated.

Is there a better and more elegant way of doing it?

Thanks and regards,

Brijesh

On Thu, Dec 15, 2016 at 5:02 PM, Rui Barradas <ruipbarradas at sapo.pt> wrote:
> Hello,
>
> That is a very common mistake. if() accepts only one TRUE/FALSE, for a
> vectorized version you need ?ifelse. Something like the following
> (untested).
>
> growth <- ifelse(diff(fyear1)==1, (exp(diff(log(df1\$sales1)))-1)*100, NA)
>
> Hope this helps,
>
>
>
> Em 15-12-2016 03:40, Brijesh Mishra escreveu:
>>
>> Hi,
>>
>> I am trying to calculate growth rate (say, sales, though it is to be
>> computed for many variables) in a panel data set. Problem is that I
>> have missing data for many firms for many years. To put it simply, I
>> have created this short dataframe (original df id much bigger)
>>
>> df1<-data.frame(co_code1=rep(c(1100, 1200, 1300), each=7),
>> fyear1=rep(1990:1996, 3), sales1=rep(seq(1000,1600, by=100),3))
>>
>> # this gives me
>> co_code1 fyear1 sales1
>> 1      1100   1990   1000
>> 2      1100   1991   1100
>> 3      1100   1992   1200
>> 4      1100   1993   1300
>> 5      1100   1994   1400
>> 6      1100   1995   1500
>> 7      1100   1996   1600
>> 8      1200   1990   1000
>> 9      1200   1991   1100
>> 10     1200   1992   1200
>> 11     1200   1993   1300
>> 12     1200   1994   1400
>> 13     1200   1995   1500
>> 14     1200   1996   1600
>> 15     1300   1990   1000
>> 16     1300   1991   1100
>> 17     1300   1992   1200
>> 18     1300   1993   1300
>> 19     1300   1994   1400
>> 20     1300   1995   1500
>> 21     1300   1996   1600
>>
>> # I am now removing a couple of rows
>> df1<-df1[-c(5, 8), ]
>> # the result is
>>     co_code1 fyear1 sales1
>> 1      1100   1990   1000
>> 2      1100   1991   1100
>> 3      1100   1992   1200
>> 4      1100   1993   1300
>> 6      1100   1995   1500
>> 7      1100   1996   1600
>> 9      1200   1991   1100
>> 10     1200   1992   1200
>> 11     1200   1993   1300
>> 12     1200   1994   1400
>> 13     1200   1995   1500
>> 14     1200   1996   1600
>> 15     1300   1990   1000
>> 16     1300   1991   1100
>> 17     1300   1992   1200
>> 18     1300   1993   1300
>> 19     1300   1994   1400
>> 20     1300   1995   1500
>> 21     1300   1996   1600
>> # so 1994 for co_code1 1100 and 1990 for co_code1 1200 have been
>> removed. If I try,
>> d<-ddply(df1,"co_code1",transform,
>> growth=c(NA,exp(diff(log(sales1)))-1)*100)
>>
>> # this apparently gives wrong results for the year 1995 (as shown
>> below) as growth rates are computed considering yearly increment.
>>
>>     co_code1 fyear1 sales1    growth
>> 1      1100   1990   1000        NA
>> 2      1100   1991   1100 10.000000
>> 3      1100   1992   1200  9.090909
>> 4      1100   1993   1300  8.333333
>> 5      1100   1995   1500 15.384615
>> 6      1100   1996   1600  6.666667
>> 7      1200   1991   1100        NA
>> 8      1200   1992   1200  9.090909
>> 9      1200   1993   1300  8.333333
>> 10     1200   1994   1400  7.692308
>> 11     1200   1995   1500  7.142857
>> 12     1200   1996   1600  6.666667
>> 13     1300   1990   1000        NA
>> 14     1300   1991   1100 10.000000
>> 15     1300   1992   1200  9.090909
>> 16     1300   1993   1300  8.333333
>> 17     1300   1994   1400  7.692308
>> 18     1300   1995   1500  7.142857
>> 19     1300   1996   1600  6.666667
>> # I thought of using the formula only when the increment of fyear1 is
>> only 1 while in a co_code1, by using this formula
>>
>> d<-ddply(df1,
>>           "co_code1",
>>           transform,
>>           if(diff(fyear1)==1){
>>             growth=(exp(diff(log(df1\$sales1)))-1)*100
>>           } else{
>>             growth=NA
>>           })
>>
>> But, this doesn't work. I am getting the following error.
>>
>> In if (diff(fyear1) == 1) { :
>>    the condition has length > 1 and only the first element will be used
>> (repeated a few times).
>>
>> # I have searched for a solution, but somehow couldn't get one. Hope
>> that some kind soul will guide me here.
>>
>> Regards,
>>
>> Brijesh K Mishra
>> Indian Institute of Management, Indore
>> India
>>
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