ol_geom_text: OpenLayers Text Layer
In cemarks/ROpenLayers: Geo-visualization Using OperLayers and ArcGIS

ol_geom_text

R Documentation

OpenLayers Text Layer

Description

Function to create a Text layer to add to an OpenLayers Map object.

Usage

ol_geom_text(point.obj, label, name = NULL, toggle.control = FALSE,
  label.params = list(), tooltip = NULL, tooltip.params = list())

Arguments

`point.obj`	SpatialPointsDataframe, SpatialPoints, or a matrix containing columns of point longitudes and latitudes, respectively.
`label`	character vector of text labels to put at points.
`name`	character Layer name.
`toggle.control`	logical indicating whether this layer will have a visibility toggle.
`label.params`	named list (e.g., `list(property=value)`) of label position and format parameters. See below.
`tooltip`	character vector of point feature tooltip popups.
`tooltip.params`	named list (e.g., `list(property=value)`) of tooltip position and format parameters. See ol_geom_polygon documentation.

Details

This function stores the data required to generate an OpenLayers vector layer with text features using Point geometries. It does not enable aesthetic mappings to variables.

Value

A list object of class Layer.Text.

Formatting Labels With `label.params`

The label.params parameter provide direct access to OpenLayers feature text styling (see OpenLayers Documentation). Multiple values for any of these properties is not supported. The following ol/style/Text properties are supported:

`font`	character label font CSS string
`offsetX`	numeric label x-offset
`offsetY`	numeric label y-offset
`rotation`	numeric label rotation
`textAlign`	character label text horizontal alighment
`textBaseline`	character label text vertical alignment
`stroke_color`	character text color
`fill_color`	character text fill color

Examples

text.pts <- matrix(
    c(
        -101.5, 39.2,
        -101.1, 54,
        -101.1, 21.4
    ),
    byrow=TRUE,
    ncol=2
)
text.labels <- c("USA","Canada","Mexico")
mymap <- ol_map(
    center=c(-100,25),
    zoom=3
) +
    oceanbase() +
    ol_geom_text(
        text.pts,
        text.labels,
        toggle.control=TRUE,
        label.params=list(
            font="16px sans-serif",
            stroke_color="#FF0000",
            fill_color="#FFFFFF00"
        )
    )
## Not run: 
# Write to file and view in browser
ol_map2HTML(mymap, "textmap.html")
browseURL("textmap.html")

## End(Not run)

cemarks/ROpenLayers documentation built on March 31, 2022, 12:05 p.m.