T-T - 4 days ago 6

R Question

I need to include some operations before summing the rows in my data frame. Here is an example:

`df1 <- data.frame(`

AC1Q = c(0.53, 0.57, 0.60, 0.51),

AC4Q = c(0.15, 0.12, 0.09,0.19),

AC2Q = c(0.09, 0.05, 0.07, 0.05),

AC3Q = c(0.23, 0.26, 0.23, 0.26)

)

df1

# AC1Q AC4Q AC2Q AC3Q

# 1 0.53 0.15 0.09 0.23

# 2 0.57 0.12 0.05 0.26

# 3 0.60 0.09 0.07 0.23

# 4 0.51 0.19 0.05 0.26

I want to get the row sums based on

`(sin(2*pi*(AC1Q-0.25)) + sin(2*pi*(-AC4Q+0.25)) - sin(2*pi*(AC2Q+0.25)) - sin(2*pi*(AC3Q-0.25)))/4)`

`# 1 0.20`

# 2 0.15

# 3 0.21

# 4 0.10

I am learning

`apply`

`apply(df1, 1, function(x) (sin(2*pi*(df1$AC1Q-0.25)) + sin(2*pi*(-df1$AC4Q+0.25)) - sin(2*pi*(-df1$AC2Q+0.25)) - sin(2*pi*(df1$AC3Q-0.25)))/4)`

`rowsum`

Answer

```
apply(df1, 1, function(x) (sin(2*pi)*(x["AC1Q"]-0.25) +
sin(2*pi)*(-x["AC4Q"]+0.25) -
sin(2*pi)*(-x["AC2Q"]+0.25) -
sin(2*pi)*(x["AC3Q"]-0.25))/4)
```

Source (Stackoverflow)

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