R语句中的复合条件

Question

My Data set contains 6 columns of which Ozone, Temp and Solar.R are a part. I need to find out the mean of Solar.R values based on condition $Ozone >31 and $Temp>90 I am executing the below code but it is returning NaN

data<-read.csv("hw1_data.csv",header=TRUE)
mean(na.omit(data[data$Ozone>31 && data$Temp>90,]$Solar.R)) 

Pls let me where I am going wrong

Answer 1

You have one to many ampersands in there.

Try:

mean(na.omit(data[data$Ozone > 31 & data$Temp > 90, ]$Solar.R))

From the help page at ?"&&" :

& and && indicate logical AND and | and || indicate logical OR . The shorter form performs elementwise comparisons in much the same way as arithmetic operators. The longer form evaluates left to right examining only the first element of each vector. Evaluation proceeds only until the result is determined. The longer form is appropriate for programming control-flow and typically preferred in if clauses.

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By the way, this pretty much sounds like the "airquality" dataset that is already available in R:

mean(na.omit(airquality[airquality$Ozone > 31 & 
                          airquality$Temp > 90, ]$Solar.R)) 
# [1] 212.8

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Oh, and doesn't using the space-bar make code much easier on the eyes?