2.16                      *******************
                                  * TOPDEL WRITE-UP *
                                  *******************
        
            TOPDEL is a program to examine/select reflection data based on the 
        magnitude of isomorphous or anomalous scattering differences.  It can 
        read in any of the "merged" files input to PHASIT and will select from 
        them data based on user supplied d spacing and F/sigma cutoffs. All 
        selected data is then sorted according to the magnitudes of the 
        differences, and the 15 largest differences are displayed along with 
        the mean and standard deviation for all selected data. Generally one 
        uses the list to identify (and reject) outliers (reflections with 
        abnormally large differences) for the purpose of Patterson map (and 
        possibly phasing) calculations. If outliers are present they usually 
        will show up as a "break" at the top of the otherwise smoothly 
        diminishing difference magnitude list. The program is interactive and 
        prompts for the names of files, type of data file input, and the d 
        spacing and F/sigma cutoffs. After displaying the list, the user is 
        prompted as to whether or not a file should be prepared for Patterson 
        map calculations. If a map is requested the user is prompted for the 
        output file name, what percentage of the selected data is to be 
        output, and how many reflections (starting from the top of the sorted 
        list) are to be rejected. Thus if 60% of the data is requested with 
        two rejections, the two largest differences are rejected and the 
        remaining largest differences are output until 60% of the total number 
        of selected reflections is reached.
        
        Note! If outliers are rejected, the rejection only applies to the 
        output Fourier file. If you want to reject the outliers from all 
        subsequent phasing calculations, you must manually edit the outliers 
        from the "merged" file input to PHASIT.   
        
        
                                   ***** FILES *****
        
        The program will prompt for the input file name and type of file input.
        The allowed types are all ASCII, read in free format and can be any of 
        the "merged" files accepted by PHASIT, i.e. records of either
        
        h, k, l, FP, Sig(FP), FPH, Sig(FPH)
        
                 or
        
        h, k, l, FP+, Sig(FP+), FP-, Sig(FP-)
        
                 or
        
        h, k, l, FP, Sig(FP), FPH+, Sig(FPH+), FPH-, Sig(FPH-)
        
        For the first type isomorphous replacement difference magnitudes 
        ABS(FP-FPH) are selected, displayed and (possibly) output. For the 
        other types anomalous scattering difference magnitudes are used 
        instead.
        
        If a Fourier output file for Patterson map calculations is requested 
        by the user a binary file will be written with 6 words per record. The 
        first three words are INTEGERS and the other three REALS. The records 
        will contain  
        
        h, k, l, FPH, FP, 0.

               or

        h, k, l, F+, F-, 0. 
        
        depending on whether isomorphous or anomalous data was input.
        
        Note that the output file can be used in FSFOUR to compute  
        either isomorphous or anomalous difference Patterson maps by setting
        MAPTYP=5. Native Patterson maps can also be computed with the file
        by setting MAPTYP=6.