offset name size contents 0 rw 2 Row 2 col 2 Column 4 ixfe 2 Index to the XF record 6 num 8 Current value of the formula 14 grbit 2 Option Flags 16 chn 4 (Reserved, must be zero) A field that specifies an application-specific cache of information. This cache exists for performance reasons only, and can be rebuilt based on information stored elsewhere in the file without affecting calculation results. 20 cce 2 Parsed Expression length 22 rgce cce Parsed ExpressionThe grbit field contains the following flags:
byte bits mask name asserted if 0 0 0x01 fAlwaysCalc the result must not be cached 1 0x02 fCalcOnLoad the cached value is incorrect 2 0x04 (Reserved) 3 0x08 fShrFmla this is a reference to a shared formula 7-4 0xF0 (Unused) 1 7-0 0xFF (Unused)In most cases, formulas should have fAlwaysCalc asserted to ensure that correct values are displayed upon opening of the file in Excel.
Before being evaluated, the following substitutions are made withing the evaluation string of a formula:
Within the context of R model formulas, a variable is any valid R expression that can be evaluated within the formula's {@link Environment} (usually adata.frame object). It is often a symbol, like simply {@code x} or {@code y}, but a variable in this context a variable can also be a function of a Symbol, such as {@code log(x)} or any valid R expression, such {@code sqrt(x/y)}.
A term is a combination of one or more variables. This class stores terms in their expanded form: the formula described by {@code y ~ a * b} actually has three terms: {@code a}, {@code b}, and {@code a:b}, where {@code a:b} is an interaction term. See {@link FormulaInterpreter} for more information on the DSL.
This internal class is used by the primitives that manipulate model formulas.
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