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Inverse Standarization

istdx.Rd

This function back transforms a standarized vector/matrix z into their original values, i.e., re-scales all the values in the [0,1] interval to the original range of values z = re-scale(x) = x*[ xmax - xmin ] + xmin.

Usage

istdx(x, ...)
# Default S3 method
istdx(x, xmin, xrange, ...)

Arguments

x

standarized vector or matrix to be re-scaled, all the values have to be in the range [0,1]

xmin

numeric with the minimum value(s) in the original x
-) if x is a vector, xmin has to be a real
-) if x is a matrix/data.frame, xmin has to be a vector, with the minimum values for each column of the original x. In this case, the vector of minimums can be obtained as: xmin <- apply(x, 2, min, na.rm=TRUE)

xrange

numeric with the range of value(s) in the original x
-) if x is a vector, xrange has to be a real
-) if x is a matrix/data.frame, xrange has to be a vector, with the range of values for each column of the original x. In this case, the vector of ranges can be obtained as:
xrange <- apply(x, 2,range, na.rm=TRUE)
xrange <- apply(xrange, 2, diff, na.rm=TRUE)

...

further arguments passed to or from other methods

Author

Mauricio Zambrano-Bigiarini, mzb.devel@gmail

See also

stdx, scale

Examples

## Loading daily streamflows at the station Oca en Ona (Ebro River basin, Spain) ##
data(OcaEnOnaQts)
x <- OcaEnOnaQts

## Computing xmin and the range of 'x'
xmin <- min(x, na.rm=TRUE)
r <- diff(range(x, na.rm=TRUE))

## Standarized variable
s <- stdx(x)

## Inverse of the standarized variable
si <- istdx(s, xmin, xrange=r)

## 'si' and 'x' should be the same
summary(x-si)
#>      Index                x - si          
#>  Min.   :1961-01-01   Min.   :-3.553e-15  
#>  1st Qu.:1961-10-01   1st Qu.: 0.000e+00  
#>  Median :1962-07-02   Median : 0.000e+00  
#>  Mean   :1962-07-02   Mean   : 1.176e-17  
#>  3rd Qu.:1963-04-01   3rd Qu.: 0.000e+00  
#>  Max.   :1963-12-31   Max.   : 3.553e-15  

###########
### Standarizing a subset of the stations 9 to 12 in 'EbroPPtsMonthly'

## Loading the monthly time series of precipitation within the Ebro River basin.
data(EbroPPtsMonthly)

pp <- EbroPPtsMonthly[1:70,10:13]
xmin   <- apply(pp, 2, min, na.rm=TRUE)
xrange <- apply(pp, 2, range, na.rm=TRUE)
xrange <- apply(xrange, 2, diff, na.rm=TRUE)

## Standarized variable
s <- stdx(as.matrix(pp))

## Inverse of the standarized variable
si <- istdx(s, xmin, xrange)

## 'si' and 'pp' should be the same
summary(pp - si)
#>      P9041                P9048                P9056           
#>  Min.   :-1.421e-14   Min.   :-1.421e-14   Min.   :-7.105e-15  
#>  1st Qu.: 0.000e+00   1st Qu.: 0.000e+00   1st Qu.: 0.000e+00  
#>  Median : 0.000e+00   Median : 0.000e+00   Median : 0.000e+00  
#>  Mean   : 1.015e-16   Mean   : 1.269e-17   Mean   : 1.523e-16  
#>  3rd Qu.: 0.000e+00   3rd Qu.: 0.000e+00   3rd Qu.: 0.000e+00  
#>  Max.   : 1.421e-14   Max.   : 1.421e-14   Max.   : 1.421e-14  
#>      P9060          
#>  Min.   :0.000e+00  
#>  1st Qu.:0.000e+00  
#>  Median :0.000e+00  
#>  Mean   :1.047e-16  
#>  3rd Qu.:0.000e+00  
#>  Max.   :7.105e-15