[R] Filter Dataframe for Alarm for particular column(s).

[arun]

Hi,
You could try ?data.table() to further increase the speed:



#Same example:
dt2<- data.table(MyDFNew)
system.time(resNew<- dt2[,lapply(.SD,function(x) {x1<-which(c(0,diff(x))<0);x1[length(x1)==0]<-0;x1})][1] )
 # user  system elapsed 
 # 0.144   0.004   0.148 
resNew
#   TNH BIX
#1:   7   2


According to this link (http://stackoverflow.com/questions/9236438/how-do-i-run-apply-on-a-data-table), using for loop should improve the speed

Regarding the use of ts() in this case, I am not very sure.

A.K.



----- Original Message -----
From: R_Antony <antony.akkara at ge.com>
To: r-help at r-project.org
Cc: 
Sent: Wednesday, July 10, 2013 1:48 AM
Subject: Re: [R] Filter Dataframe for Alarm for particular column(s).

Hi Arun,



Thanks for the solution it  really works !. But how can we avoid even lappy() and  sappy().

Actually any way to do with ts() ?

Thanks,

Antony.



From: arun kirshna [via R] [mailto:ml-node+s789695n4670970h8 at n4.nabble.com] 
Sent: Saturday, July 06, 2013 12:54 AM
To: Akkara, Antony (GE Power & Water, Non-GE)
Subject: Re: Filter Dataframe for Alarm for particular column(s).



Hi, 
May be this helps: 
If you had showed your solution, it would be easier to compare. 

res<-data.frame(lapply(sapply(MyDF[,c(2,4)],function(x) {x1<-which(c(0,diff(x))<0);x1[length(x1)==0]<-0;x1}),`[`,1)) 
res 
#  TNH BIX 
#1   3   9 


#Speed 

set.seed(24) 
MyDFNew<- data.frame(TNH=sample(0:1,1e6,replace=TRUE),BIX=sample(0:1,1e6,replace=TRUE)) 
system.time(res1<-data.frame(lapply(sapply(MyDFNew,function(x) {x1<-which(c(0,diff(x))<0);x1[length(x1)==0]<-0;x1}),`[`,1))) 
#   user  system elapsed 
#  0.364   0.000   0.363 

res1 
#  TNH BIX 
#1   7   2 
MyDFNew[1:10,] 
#   TNH BIX 
#1    0   1 
#2    0   0 
#3    1   1 
#4    1   1 
#5    1   0 
#6    1   0 
#7    0   1 
#8    1   1 
#9    1   1 
#10   0   0 


A.K. 


Hi, 


Hi here i have a dataframe called MyDF. 

a<-c(1,1,1,1,1,0,0,0,1,1) 
b<-c(1,1,0,1,1,0,0,0,1,1) 
c<-c(1,1,1,1,1,1,1,0,1,1) 
d<-c(1,1,1,1,1,1,1,1,0,1) 
MyDF<-data.frame(DWATT=a,TNH=b,CSGV=c,BIX=d) 

My requirement is, here i need a function - to get for a 
particular row number(s), when particular column(s) value change from 
one-to-zero  (for the first change). Suppose there is no change is 
happening then it should return "Zero" 

For example,  Using MyDF, 

DWATT TNH CSGV BIX 
1   1    1   1 
1   1    1   1 
1   0    1   1 
1   1    1   1 
1   1    1   1 
0   0    1   1 
0   0    1   1 
0   0    0   1 
1   1    1   0 
1   1    1   1 

Here i want to know, the row number where TNH-column and BIX-column values change happening from one-to-zero for the first time. 

Note:- Suppose there is no change is happening then it should return "Zero" 

Answer should be  a dataframe with single row. 
So here answer should return a dataframe like this. 

TNH  BIX 
----    ------ 
3      9 


i used some ways to get a solution using loops. But there is a bulk files with bulk rows to process. 
So performace is most important. Could someone please suggest better ideas ? 

Thanks, 
Antony. 

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