R: Convert to Probability / Category Forecast

convert2prob {easyVerification} | R Documentation

## Convert to Probability / Category Forecast

### Description

`convert2prob` Converts the continuous ensemble forecast to counts of ensemble members per category. The categories can be defined relative to the ensemble distribution (using `prob`) or relative to absolute values for the category thresholds (using `threshold`, see details). `prob2thresh` converts the relative threshold to absolute thresholds for later processing. `expandthresh` expands the vector or matrix of thresholds to fit the input data.

### Usage

    convert2prob(x, prob = NULL, threshold = NULL, ref.ind = NULL,
      multi.model = FALSE)

    prob2thresh(x, prob, ref.ind = NULL, multi.model = FALSE)

    expandthresh(threshold, x)

### Arguments

`x` | input vector or matrix
`prob` | thresholds for categorical forecasts (defaults to NULL)
`threshold` | absolute thresholds for categorical forecasts (defaults to NULL)
`ref.ind` | list of forecast/obs instances to be used to estimate percentile thresholds
`multi.model` | logical, are we dealing with initial condition (the default) or multi-model ensembles (see details)?

### Details

In case both `prob` and `threshold` are set to `NULL`, the function returns the input `x` without modification. If `prob` is set, a matrix with the number of occurrences per class for a given quantile of the full distribution (e.g. temperature above/below the median). If `threshold` is set, the classes are defined based on the absolute value (e.g. temperature above/below 13 deg. C). Multiple classes are

Only certain formats of `threshold` and `prob` are supported. `prob` has to be a vector with percentile thresholds separating the different classes. `threshold` can be a vector, matrix or array with the first entry corresponding to the different classes, and the last to the different ensemble members (if present). Thereby, time/forecast varying thresholds can potentially be supplied (although I am not sure this is useful or needed).

If `ref.ind` is specified, only the specified indices of the input variables are used to estimate the percentile thresholds (`prob`). If used with `threshold`, or without anything, `ref.ind` has no effect.

If `multi.model = TRUE`, the relative thresholds supplied by `prob` are ensemble member specific, i.e. are estimated for each ensemble member separately. This is in particular applicable for multi-model ensembles with model dependent biases.

### Value

Matrix of occurrences per class (i.e. the number of ensemble members per class, or an indicator for the observations)

### See Also

`veriApply`

### Examples

    tm <- toymodel()

    ## convert to tercile forecasts (only display first forecast and obs)
    convert2prob(tm$fcst, prob=1:2/3)[1,]
    convert2prob(tm$obs, prob=1:2/3)[1,]

    ## convert to category forecasts (smaller and larger than 1)
    convert2prob(tm$fcst, threshold=1)[1,]
    convert2prob(tm$obs, threshold=1)[1,]

[Package easyVerification version 0.4.4 Index]