Calculate means for horizontal and vertical directions

Calculate means for horizontal and vertical directions for mapping data.

hmean(x, cluster = NULL, density = NULL, ..., .by = "y")

vmean(x, cluster = NULL, density = NULL, ..., .by = "x")

Arguments

x	A `qntmap` class object returned by `quantify()` or `qntmap()`.
cluster	A result of `cluster_xmap()` (i.e., `qm_cluster` class object). `cluster` is required when specifying `density`.
density	A named numeric vector specifying density of all the phases in `x`. (e.g., `c(Qtz = 2.6, Ab = 2.6)`).
...	Ignored
.by	Internal use. Do not change. "y" for `hmean` to calculate mean from pixels with same `y`-coordinates, and "x" for `vmean` to calculate mean from pixels with same `x`-coordinates.