I would like to change some values of some particular rows. According to previous questions that seemed straight forward with `df[df$column=="value",]<-"new value"`
However I get error `character string is not in a standard unambiguous format`
applying that:

Some data:

```
dates <- seq(as.Date("2015-02-13"), as.Date("2015-02-22"), by = "days")
b <- c("one","one","two","two","four","four","one","one","five","five")
c <- c(20,30,26,20,30,40,5,10,4,0)
d <- c(11,2233,12,2,22,13,23,23,100,1)
df <- data.frame(dates,b,c,d)

```

I just would like change all ones to seven:

```
df[df$b=="one",]<-"seven"

```

character string is not in a standard unambiguous format