next up previous contents index
Next: Requirements Up: Manipulating Reflection Data Previous: Manipulating Reflection Data

Syntax

DO <xrefin-do-statement>
is invoked as an xrefin statement. Action takes place as soon as the construct is complete.
<xrefin-do-statement>:==
<xrefin-do-mode> ( <xrefin-property> = <xrefin-do-expression> )
<xrefin-do-mode>:==
AMPLitude
carries out an operation using amplitudes of xrefin properties.
COMPlex
carries out an operation in complex space.
PHASe
carries out an operation using phases of xrefin properties. Phases are manipulated in degrees.
SCALe
    involves an operation that multiplies the left-hand side (lhs) by a scale factor k, which is defined as

where rhs represents the right-hand side of the equation. The action of this statement is identical to the scaling carried out when computing the R value or the residual (cf. Eqs. 12.1, 12.6), except that it refers the scaling to the right-hand side of the equation, whereas in the residual or R value evaluation the scaling refers to . Therefore, if the right-hand side of the scaling operation consists of , the program refers only to but not to to .

<xrefin-do-expression>:==
<xrefin-vflc> [ <op>
<xrefin-do-expression> ]
represents a mathematical operation and is defined in Section 2.16.
<xrefin-vflc>:==
<function>
| <xrefin-function> | <symbol> | <real> | <integer> | <complex> | <xrefin-property> represents mathematical functions and is defined in Section 2.16. Special xrefin functions are defined below. The data type of the function arguments has to match the data type of the operands.

<xrefin-property>:==
FCALC
specifies calculated structure factors (complex).
FOBS
specifies observed structure factors (complex).
FPART
specifies partial structure factors (complex).
SIGMA
specifies values (real).
TEST
is an array for cross-validation that allows one to compute the free R value (see Chapter 15).
WEIGHT
specifies weights (real).

<xrefin-function>:==
H()
defines an array that consists of the Miller index h.
K()
defines an array that consists of the Miller index k.
L()
defines an array that consists of the Miller index l.
S()
defines an array that consists of the length of the reciprocal lattice vector for each reflection h,k,l.



next up previous contents index
Next: Requirements Up: Manipulating Reflection Data Previous: Manipulating Reflection Data



Sat Mar 11 09:37:37 PST 1995