Identifier     sap_log

 Purpose        Perform y = log(x) on arrays (natural logarithm)
                (with error propagation)

 Synopsis       sap_log, arr_in, sarr_in, arr_out, sarr_out

 Arguments      Name      I/O  Type      Description
                -----------------------------------------------------
                arr_in    I    Float(*)  input array (e.g. flux)
                sarr-in   I    Float(*)  array of uncertainties for arr_in 
                sarr_out  O    Float(*)  array of uncertainties for arr_out
                                         (propagated errors)
                arr_out   O    Float(*)  output array

 Returns        arr_out = log(arr_in), 
                sarr_out= propagated error

 Description    

 Comment        The routine is usually called from the "shell" ARITHM

 Example        log, aar.data.flux, aar.data.stdev, log_arr, log_stdev

 Dependencies   CALLS: sap_error
                CALLED FROM: arithm

 Category       ISAP

 Filename       sap_log.pro

 Author         A. Fiedler (--> AF)

 Version        1.0
                              
 History        0.1   27-09-95  AF 
                1.0   30-11-95  ES V1 delivery
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Copyright (C) 1995, Max-Planck-Institut fuer extraterrestrische Physik (MPE);
                    Garching, Germany                                       ;
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