# tests/testthat/test-coordinates.R In kinematics: Studying Sampled Trajectories

```context('Coordinates')

test_that('Polar coordinates (no shift)', {
# Create some points in cartesian coordinates
xs <- c(0, 0, 1, 2)
ys <- c(0, 1, 1, 2)

# The expected polar coordinates are
rs_expected <-  c(0, 1,    sqrt(2), sqrt(8))
ths_expected <- c(0, pi/2, pi/4,    pi/4)

# Calculate using the function
p <- get_polar_coordinates(xs, ys)

# Check that the results match
expect_equal(rs_expected, p\$r)
expect_equal(ths_expected, p\$th)
})

test_that('Polar coordinates (with shift)', {
# Create some points in cartesian coordinates
xs <- c(0, 0, 1, 2) + 2
ys <- c(0, 1, 1, 2) + 1

# The expected polar coordinates are
rs_expected <-  c(0, 1,    sqrt(2), sqrt(8))
ths_expected <- c(0, pi/2, pi/4,    pi/4)

# Calculate using the function
p <- get_polar_coordinates(xs, ys, origin = c(2, 1))

# Check that the results match
expect_equal(rs_expected, p\$r)
expect_equal(ths_expected, p\$th)
})
```

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kinematics documentation built on July 19, 2021, 9:07 a.m.