R: Align positions using length.

compute_align {ggvis} | R Documentation

## Align positions using length.

### Description

This compute function is often used in conjunction with `compute_count`, when used on data with a continuous x variable. By default, the computed width will be equal to the resolution of the data, or, in other words the smallest difference between two values in the data.

### Usage

    compute_align(x, var, length = NULL, align = 0.5, dir = "x")

### Arguments

`x` | Dataset-like object to align. Built-in methods for data frames, grouped data frames and ggvis visualisations.
`var` | Name of variable to compute width of.
`length` | An absolute length to use. If `NULL` (the default), the width will be equivalent to the resolution of the data.
`align` | Where does the existing variable fall on the new bins? 0 = left edge, 0.5 = center, 1 = right edge.
`dir` | Direction, i.e. `"x"` or `"y"`. Used to generate variable names in output.

### Details

An absolute width for each x can be specified by using the `width` argument. If `width` is NULL (the default), it will use the resolution of the data as the width.

### Value

The original data frame, with additional columns:

`'dir'min_` | left boundary of bin
`'dir'max_` | right boundary of bin
`'dir'len_` | width of bin

### See Also

`compute_bin` For counting cases within ranges of a continuous variable.

`compute_count` For counting cases at specific values of a variable.

### Examples

    mtcars %>% compute_count(~disp) %>% compute_align(~x_)
    mtcars %>% compute_count(~mpg) %>% compute_align(~x_)

    # Use a specific width
    pressure %>% compute_count(~temperature) %>% compute_align(~x_)
    pressure %>% compute_count(~temperature) %>% compute_align(~x_, length = 5)

    # It doesn't matter whether you transform inside or outside of a vis
    mtcars %>% compute_count(~cyl, ~wt) %>%
      compute_align(~x_, length = .5) %>%
      ggvis(x = ~xmin_, x2 = ~xmax_, y = ~count_, y2 = 0) %>%
      layer_rects()

    mtcars %>%
      ggvis(x = ~xmin_, x2 = ~xmax_, y = ~count_, y2 = 0) %>%
      compute_count(~cyl, ~wt) %>%
      compute_align(~x_) %>%
      layer_rects()

    # Varying align
    mtcars %>%
      ggvis(x = ~xmin_, x2 = ~xmax_, y = ~count_, y2 = 0) %>%
      compute_count(~cyl, ~wt) %>%
      compute_align(~x_, length = 0.5, align = input_slider(0, 1)) %>%
      layer_rects()

[Package ggvis version 0.4.3 Index]