How to find in R the vector of all values between two 3D points?-CodePudding

I have two 3D points:

t0: [5,1,8], t200: [100,20,10]

I have to find the line between t0 and t200 and all 3D points (x,y,z) included between t0 and t200. Finally, plot it and create a dataframe like this:

       x    y    z
t0     5    1    9
t1
...
t200   100  20   10

Any tip?

best regards

CodePudding user response：

Using mapply and fast seq.int.

mapply(\(x, y) seq.int(x, y, length.out=201), t0, t200)

And the data frame:

res <- mapply(\(x, y) seq.int(x, y, length.out=201), t0, t200) |>
  `dimnames<-`(list(paste0('t', 0:200), letters[24:26])) |>
  as.data.frame() 

head(res)
#        x     y    z
# t0 5.000 1.000 0.00
# t1 5.475 1.095 0.05
# t2 5.950 1.190 0.10
# t3 6.425 1.285 0.15
# t4 6.900 1.380 0.20
# t5 7.375 1.475 0.25

tail(res)
#             x     y    z
# t195  97.625 19.525  9.75
# t196  98.100 19.620  9.80
# t197  98.575 19.715  9.85
# t198  99.050 19.810  9.90
# t199  99.525 19.905  9.95
# t200 100.000 20.000 10.00

Note: R >= 4.1

Data:

t0 <- c(5, 1, 0)
t200 <- c(100, 20, 10)

CodePudding user response：

Assuming you want a vector between t0 and t200, you could just use seq with the same n

start <- c(5, 1, 9)
end <- c(100, 20, 10)
n <- 201
sapply(1:3, \(i) seq(start[i], end[i], length = n))

A faster method would be to invert the normalization formula x_norm = (x - x_min) / (x_max - x_min) <=> x = x_norm * (x_max - x_min) x_min

x_i <- seq(0, 1, length = n)
sapply(1:3, \(i)x_i * (end[i] - start[i])   start[i])

all.equal(sapply(1:3, \(i) seq(start[i], end[i], length = n)), 
          sapply(1:3, \(i)x_i * (end[i] - start[i])   start[i]))
[1] TRUE