I have a dataframe called `mat.new`

. Here's how to generate this data:

```
year <- rep(1980:2015, each = 365)
doy <- rep(1:365, times = 36)
set.seed(125)
val <- sample(0:1, size = 365*36,replace = TRUE)
mat <- as.matrix(cbind(year,doy,val))
mat <- as.data.frame(mat)
mat <- mat %>%
mutate(doy1 = rep(1:730, times = 18))
mat <- mat[,c(1:2,4,3)]
set.seed(123)
mat1 <- apply(matrix(sample(c(230:365), replace = TRUE, size = 2L * 36L), nrow = 36L), 2L, sort)
mat1 <- t(apply(mat1, 1, function(x) x[order(x)]))
colnames(mat1) <- c("D1", "D2")
mat1 <- cbind(year = 1980:2015, mat1)
mat1 <- as.data.frame(mat1)
mat1[1:6,3] <- 5:10
mat1 <- mat1 %>%
mutate(D2 = ifelse(D1 > D2, D2 + 365, D2))
mat_new <- mat %>%
left_join(mat1, by = "year")
```

`mat_new`

has six columns. Column 1 = year, Column 2: `doy`

(365 days each year), column 3 = `doy1`

but goes from 1 till 730 ( 2 years) and repeats again from 1 to 730. Column 4 has some value (`val`

), column 5 and 6 has a certain start (`D1`

) and end doy (`D2`

) of each year. If `D2`

> 365, this implies the end date was next year. For e.g. for 1980, the end date is 370 which is the 5th day of 1981,

I need to subset `val`

for each year based on their respective start and end doy. For e.g for 1980, the `val`

I need to subset should start from 233 of 1980 till 5th of 1981 (370 is the end date). I thought of first creating another column with true and false which I can then use to subet the `val`

```
mat_new1 <- mat_new %>%
mutate(group1 = ifelse(D2 <= 365, doy >= D1 & doy <= D2 , doy >= D1 & doy1 <= D2))
```

The above line should create another column `group1`

with TRUE and FALSE. If `D2`

<= 365 i.e. the end date falls within the same year, use the `doy`

column to subset `D1`

till `D2`

. However, if `D2`

is
in the next year (D2 > 365), then use `doy`

as start date and take the end date from `doy1`

column. The above function, however for 1980 (and other years)
only puts TRUE starting the `D1`

but ends at 365 for 1980 instead of going to 5th Jan of 1981 (370 from `doy1`

)

What am I doing wrong here?