Generate data frame of band summary statistics and class pixel counts
Usage
describeChips(
folder,
extension = ".tif",
mode = "All",
subSample = TRUE,
numChips = 200,
numChipsBack = 200,
subSamplePix = TRUE,
sampsPerChip = 100
)Arguments
- folder
Full folder path or folder path relative to the current working directory that holds the image chips and associated masks. You must include the final forward slash in the folder path (e.g., "C:/data/chips/").
- extension
Raster file extension (e.g., ".tif", ".png", ".jpeg", or ".img"). The utilities in this package generate files in ".tif" format, so this is the default. This option is provided if chips are generated using another method.
- mode
Either "All", "Positive", or "Divided". This should match the settings used in the makeChips() function or be set to "All" if makeChipsMultiClass() is used. Default is "All".
- subSample
TRUE or FALSE. Whether or not to subsample the image chips to calculate the summary metrics. We recommend using a subset if a large set of chips are being summarized to reduce computational load. The default is TRUE.
- numChips
If subSample is set to TRUE, this parameter defines the number of chips to subset. The default is 200. This parameter will be ignored if subSample is set to FALSE.
- numChipsBack
If subSample is set to TRUE and the mode is "Divided", this parameter indicates the number of chips to sample from the background-only samples. The default is 200. This parameter will be ignored if subSample is set to FALSE and/or mode is not "Divided".
- subSamplePix
TRUE or FALSE. Whether or not to calculate statistics using a subsample of pixels from each image chip as opposed to all pixels. If a large number of chips are available and/or each chip is large, we suggest setting this argument to TRUE to reduce the computational load. The default is TRUE.
- sampsPerChip
If subSamplePix is TRUE, this parameters specifies the number of random pixels to sample per chip. The default is 100. If subSamplePix is set to FALSE, this parameter is ignored.
Value
List object containing the summary metrics for each band in the $ImageStats object and the count of pixels by class in the $maskStats object.
Details
This function generates a set of summary metrics from image chips and associated masks stored in a directory. For each band, the minimum, median, mean, maximum, and standard deviation are returned (along with some other metrics). For mask data, the count of pixels in each class are returned. These summarizations can be useful for data normalization and determining class weightings in loss calculations.