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Get count by day for particular coulmn

2 messages · R_Antony, Sarah Goslee

R_Antony
# 
here i have a dataframe 

for eg:-
DATETIME	COL_A	COL_B	COL_C	COL_D
1/1/2007 0:01	0	3	0	0
1/1/2007 0:02	0	0	3	0
1/1/2007 0:03	0	3	0	0
.......................       .....             ...             ...             
....				
1/2/2007	0	0	3	0
1/2/2007 0:01	0	3	4	0
1/2/2007 0:02	0	3	0	0
.......................       .....             ...             ...             
....
1/3/2007	0	0	0	0
1/3/2007 0:01	0	0	4	0
1/3/2007 0:02	0	3	0	0
.......................       .....             ...             ...             
....

My requirement what is, i have to get the count for each "day " where COL_B
= 3

For eg:- here i need to get like
DATETIME           COUNT(COL_B=3)
------------            ------------
1/1/2007               2
1/2/2007               3
1/3/2007               1

=============================
=============================

and this way i tried to get,
MyDF[MyDF["DATETIME"]=="1/2/2007"]  ---> here this only select the row where
DATETIME - column coming as
"1/2/2007" - date and not selecting other rows where same date is coming
(eg:- 1/1/2007 0:01). And here i need to get the complete records for that
particular day, when i give date without giving timestamp. 

- Could anyone give a help ASAP ?

- Thanks
Antony.





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Sarah Goslee
# 
Hi,
On Fri, Jun 7, 2013 at 7:38 AM, R_Antony <antony.akkara at ge.com> wrote:
Since you didn't provide reproducible data (dput() is great for that),
here's an example with fake data:


MyDF <- data.frame(DATETIME = c("1/1/2007", "1/1/2007", "1/1/2007",
"1/2/2007", "1/2/2007", "1/2/2007", "1/3/2007", "1/3/2007",
"1/3/2007"),
COL_A = c(0, 0, 0, 1, 0, 1, 2, 3, 1),
COL_B = c(0, 3, 0, 3, 3, 1, 0, 1, 2),
COL_C = c(1, 2, 3, 1, 2, 3, 1, 2, 3), stringsAsFactors=FALSE)

aggregate(COL_B ~ DATETIME, data=MyDF, FUN=function(x)sum(x == 3))
You omitted a comma:
MyDF[MyDF["DATETIME"]=="1/2/2007", ]


You might prefer:
subset(MyDF, DATETIME == "1/2/2007")

Sarah