R: Examples for 'stats::poly'

### ** Examples

od <- options(digits = 3) # avoid too much visual clutter
(z <- poly(1:10, 3))

           1      2      3
 [1,] -0.495  0.522 -0.453
 [2,] -0.385  0.174  0.151
 [3,] -0.275 -0.087  0.378
 [4,] -0.165 -0.261  0.335
 [5,] -0.055 -0.348  0.130
 [6,]  0.055 -0.348 -0.130
 [7,]  0.165 -0.261 -0.335
 [8,]  0.275 -0.087 -0.378
 [9,]  0.385  0.174 -0.151
[10,]  0.495  0.522  0.453
attr(,"coefs")
attr(,"coefs")$alpha
[1] 5.5 5.5 5.5

attr(,"coefs")$norm2
[1]    1.0   10.0   82.5  528.0 3088.8

attr(,"degree")
[1] 1 2 3
attr(,"class")
[1] "poly"   "matrix"

predict(z, seq(2, 4, 0.5))

          1       2     3
[1,] -0.385  0.1741 0.151
[2,] -0.330  0.0326 0.305
[3,] -0.275 -0.0870 0.378
[4,] -0.220 -0.1850 0.383
[5,] -0.165 -0.2611 0.335

zapsmall(poly(seq(4, 6, 0.5), 3, coefs = attr(z, "coefs")))

          1      2      3
[1,] -0.165 -0.261  0.335
[2,] -0.110 -0.316  0.246
[3,] -0.055 -0.348  0.130
[4,]  0.000 -0.359  0.000
[5,]  0.055 -0.348 -0.130
attr(,"coefs")
attr(,"coefs")$alpha
[1] 5.5 5.5 5.5

attr(,"coefs")$norm2
[1]    1.0   10.0   82.5  528.0 3088.8

attr(,"degree")
[1] 1 2 3
attr(,"class")
[1] "poly"   "matrix"

 zm <- zapsmall(polym (    1:4, c(1, 4:6),  degree = 3)) # or just poly():
(z1 <- zapsmall(poly(cbind(1:4, c(1, 4:6)), degree = 3)))

        1.0  2.0    3.0    0.1   1.1    2.1    0.2    1.2    0.3
[1,] -0.671  0.5 -0.224 -0.802 0.538 -0.401  0.323 -0.217 -0.053
[2,] -0.224 -0.5  0.671  0.000 0.000  0.000 -0.688  0.154  0.526
[3,]  0.224 -0.5 -0.671  0.267 0.060 -0.134 -0.239 -0.053 -0.788
[4,]  0.671  0.5  0.224  0.535 0.359  0.267  0.604  0.405  0.315
attr(,"degree")
[1] 1 2 3 1 2 3 2 3 3
attr(,"coefs")
attr(,"coefs")[[1]]
attr(,"coefs")[[1]]$alpha
[1] 2.5 2.5 2.5

attr(,"coefs")[[1]]$norm2
[1] 1.0 4.0 5.0 4.0 1.8


attr(,"coefs")[[2]]
attr(,"coefs")[[2]]$alpha
[1] 4.00 2.71 4.47

attr(,"coefs")[[2]]$norm2
[1]  1.00  4.00 14.00 25.86  9.94


attr(,"class")
[1] "poly"   "matrix"

## they are the same :
stopifnot(all.equal(zm, z1, tolerance = 1e-15))

## poly(<matrix>, df) --- used to fail till July 14 (vive la France!), 2017:
m2 <- cbind(1:4, c(1, 4:6))
pm2 <- zapsmall(poly(m2, 3)) # "unnamed degree = 3"
stopifnot(all.equal(pm2, zm, tolerance = 1e-15))

options(od)

Examples for 'stats::poly'

Compute Orthogonal Polynomials