Delete rows with specific values by keeping first and last row of dataframe

Question

I have a dataframe which made by appending similar dataframes. sample file https://drive.google.com/open?id=0BwswfhTezOETWmpPakpGOUl0V0E

Lat Lon Species BottomDepth RunStatus
6023.9796   518.5393        NA   TowStarted 
6023.9796   518.5393     Cucumber   25    
6023.9796   518.5393     Cucumber   25     
6023.9796   518.5392     Chank  25     
6023.9797   518.5392        NA   TowStarted 
6023.9797   518.5392        NA   TowStopped 
6023.9797   518.5392     Cucumber   29     
6023.9797   518.5392     Chank  29     
6023.9797   518.5392     Chank  29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391        NA   TowStarted 
6023.9797   518.5391        NA   TowStopped 
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Cucumber   29     
6023.9797   518.5391        NA   TowStarted 
6023.9797   518.5391        NA   TowStopped 
6023.9797   518.5391     Cucumber   29     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Chank  35     
6023.9797   518.5391        NA   TowStopped 

I need to keep first and last rows. but need to delete rows with RunStatus=="TowStarted" and RunStatus=="TowStopped".

mf<- read.csv("C:/Video_sledge/Output/merge.csv")
mf1 <-mf[ !grepl("TowStarted", mf$RunStatus) , ]
mf2 <-mf1[ !grepl("TowStopped", mf1$RunStatus) , ]

but this code deletes first and last rows.

How delete middle rows with test condition (RunStatus=="TowStarted" and RunStatus=="TowStopped") while keeping first and last rows?

expected output as follows

Lat Lon Species BottomDepth RunStatus
6023.9796   518.5393        NA   TowStarted 
6023.9796   518.5393     Cucumber   25    
6023.9796   518.5393     Cucumber   25     
6023.9796   518.5392     Chank  25     
6023.9797   518.5392     Cucumber   29     
6023.9797   518.5392     Chank  29     
6023.9797   518.5392     Chank  29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Sea Urchine    29     
6023.9797   518.5391     Cucumber   29     
6023.9797   518.5391     Cucumber   29     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Cucumber   35     
6023.9797   518.5391     Chank  35     
6023.9797   518.5391        NA   TowStopped

Answer 1

mf[c(1,which(!(mf$RunStatus %in% c(" TowStarted "," TowStopped "))),nrow(mf)),]

Answer 2

You could use the dplyr package

library(dplyr)
library(magrittr)

df %>% 
  filter(!(RunStatus %in% c("TowStarted", "TowStopped")) | row_number() %in% c(1, nrow(df)))

I tested it on other data and it worked.

Answer 3

mf<- read.csv("C:/Video_sledge/Output/merge.csv")
frow <- mf[1,]
mf1 <-mf[ !grepl("TowStarted", mf$RunStatus) , ]
mf2 <-mf1[ !grepl("TowStopped", mf1$RunStatus) , ]
lrow <- mf[nrow(mf),]
f <-rbind(frow,mf2,lrow)

this code gives me above output. but I think someone has a better solution.