How to check if subset is empty in R - r

Question

I have a set of data with weight with time (t), I need to identify outliers of weight for every time (t), after which I need to send a notification email.
I'm using bloxplot($out) to identify the outliers, it seems to work, but I'm not sure if:
It's the correct way to use the boxplot?
I can't detect if the boxplot has no outlier or if its empty (or maybe, I'm using a wrong technique)
Or possibly the subset itself is empty (could be the root cause)
For now, I just need to trap the empty subset and check if out variable is empty or not.
Below is my R script code:
#i am a comment, and the compiler doesn't care about me
#load our libraries
library(ggplot2)
library(mailR)
#some variables to be used later
from<-""
to<-""
getwd()
setwd("C:\\Temp\\rwork")
#read the data file into a data(d) variable
d<-read.csv("testdata.csv", header=TRUE) #file
#get the current time(t)
t <-format(Sys.time(),"%H")
#create a subset of d based on t
sbset<-subset(d,Time==t)
#identify if outlier exists then send an email report
out<-boxplot(sbset$weight)$out
if(length(out)!=0){
#create a boxplot of the subset
boxplot(sbset$weight)
subject = paste("Attention: An Outlier is detected for Scheduled Job Run on Hour ",t)
message = toString(out) #sort(out)
}else{
subject = paste("No Outlier Identified")
message = ""
}
email<-send.mail(from=from,
to=to,
subject=subject,
body=message,
html=T,
smtp=list(host.name = "smtp.gmail.com",
port = 465,
user.name = from,
passwd = "", #password of sender email
ssl = TRUE),
authenticate=TRUE,
send=TRUE)
DATA
weight,Time,Chick,x
42,0,1,1
51,2,1,1
59,4,1,1
64,6,1,1
76,8,1,1
93,10,1,1
106,12,1,1
125,14,1,1
149,16,1,1
171,18,1,1
199,20,1,1
205,21,1,1
40,0,2,1
49,2,2,1
58,4,2,1
72,6,2,1
84,8,2,1
103,10,2,1
122,12,2,1
138,14,2,1
162,16,2,1
187,18,2,1
209,20,2,1
215,21,2,1
43,0,3,1
39,2,3,1
55,4,3,1
67,6,3,1
84,8,3,1
99,10,3,1
115,12,3,1
138,14,3,1
163,16,3,1
187,18,3,1
198,20,3,1
202,21,3,1
42,0,4,1
49,2,4,1
56,4,4,1
67,6,4,1
74,8,4,1
87,10,4,1
102,12,4,1
108,14,4,1
136,16,4,1
154,18,4,1
160,20,4,1
157,21,4,1
41,0,5,1
42,2,5,1
48,4,5,1
60,6,5,1
79,8,5,1
106,10,5,1
141,12,5,1
164,14,5,1
197,16,5,1
199,18,5,1
220,20,5,1
223,21,5,1
41,0,6,1
49,2,6,1
59,4,6,1
74,6,6,1
97,8,6,1
124,10,6,1
141,12,6,1
148,14,6,1
155,16,6,1
160,18,6,1
160,20,6,1
157,21,6,1
41,0,7,1
49,2,7,1
57,4,7,1
71,6,7,1
89,8,7,1
112,10,7,1
146,12,7,1
174,14,7,1
218,16,7,1
250,18,7,1
288,20,7,1
305,21,7,1
42,0,8,1
50,2,8,1
61,4,8,1
71,6,8,1
84,8,8,1
93,10,8,1
110,12,8,1
116,14,8,1
126,16,8,1
134,18,8,1
125,20,8,1
42,0,9,1
51,2,9,1
59,4,9,1
68,6,9,1
85,8,9,1
96,10,9,1
90,12,9,1
92,14,9,1
93,16,9,1
100,18,9,1
100,20,9,1
98,21,9,1
41,0,10,1
44,2,10,1
52,4,10,1
63,6,10,1
74,8,10,1
81,10,10,1
89,12,10,1
96,14,10,1
101,16,10,1
112,18,10,1
120,20,10,1
124,21,10,1
43,0,11,1
51,2,11,1
63,4,11,1
84,6,11,1
112,8,11,1
139,10,11,1
168,12,11,1
177,14,11,1
182,16,11,1
184,18,11,1
181,20,11,1
175,21,11,1
41,0,12,1
49,2,12,1
56,4,12,1
62,6,12,1
72,8,12,1
88,10,12,1
119,12,12,1
135,14,12,1
162,16,12,1
185,18,12,1
195,20,12,1
205,21,12,1
41,0,13,1
48,2,13,1
53,4,13,1
60,6,13,1
65,8,13,1
67,10,13,1
71,12,13,1
70,14,13,1
71,16,13,1
81,18,13,1
91,20,13,1
96,21,13,1
41,0,14,1
49,2,14,1
62,4,14,1
79,6,14,1
101,8,14,1
128,10,14,1
164,12,14,1
192,14,14,1
227,16,14,1
248,18,14,1
259,20,14,1
266,21,14,1
41,0,15,1
49,2,15,1
56,4,15,1
64,6,15,1
68,8,15,1
68,10,15,1
67,12,15,1
68,14,15,1
41,0,16,1
45,2,16,1
49,4,16,1
51,6,16,1
57,8,16,1
51,10,16,1
54,12,16,1
42,0,17,1
51,2,17,1
61,4,17,1
72,6,17,1
83,8,17,1
89,10,17,1
98,12,17,1
103,14,17,1
113,16,17,1
123,18,17,1
133,20,17,1
142,21,17,1
39,0,18,1
35,2,18,1
43,0,19,1
48,2,19,1
55,4,19,1
62,6,19,1
65,8,19,1
71,10,19,1
82,12,19,1
88,14,19,1
106,16,19,1
120,18,19,1
144,20,19,1
157,21,19,1
41,0,20,1
47,2,20,1
54,4,20,1
58,6,20,1
65,8,20,1
73,10,20,1
77,12,20,1
89,14,20,1
98,16,20,1
107,18,20,1
115,20,20,1
117,21,20,1
40,0,21,2
50,2,21,2
62,4,21,2
86,6,21,2
125,8,21,2
163,10,21,2
217,12,21,2
240,14,21,2
275,16,21,2
307,18,21,2
318,20,21,2
331,21,21,2
41,0,22,2
55,2,22,2
64,4,22,2
77,6,22,2
90,8,22,2
95,10,22,2
108,12,22,2
111,14,22,2
131,16,22,2
148,18,22,2
164,20,22,2
167,21,22,2
43,0,23,2
52,2,23,2
61,4,23,2
73,6,23,2
90,8,23,2

Answer 1

Your first use of boxplot is unnecessarily creating a plot, you can use
out <- boxplot.stats(sbset$weight)$out
for a little efficiency.
You are interested in the presence of rows, but length(sbset) will return the number of columns. I suggest instead nrow or NROW.
if (NROW(out) > 0) {
boxplot(sbset$weight)
# ...
} else {
# ...
}