The Variant Data Type

The Variant data type is the default data type in VBA. Like Excel itself, the Variant data type handles and interconverts between many different kinds of data integer, floating point, string, etc. The Variant data type automatically chooses the most compact representation. But if your procedure deals with only one kind of data, it will be more efficient and usually faster to declare the variables as, for example. Integer. 

Data type Storage required Range of values 

Single precision 4 bytes -3.402823E38 to -1.401298E 5 for negative values 1.401298E-45 to 3.402823E38 for positive values 

Double precision 8 bytes -1.79769313486232E308 to. 94065645841247E-324 for negative values 4.94065645841247E-324 to 1.79769313486232E308 for positive values 

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VBA uses the Variant data type as the default data type for variables and arguments. The Variant data type permits Excel to switch between floatingpoint, integer and string variables as required. 

You can also specify the data type of the return value. If none is specified, the Variant data type will be returned. In the example of the preceding section, MolWt returns a floating-point result. The Variant data type is satisfactory ... 

Finally, in the advanced section of the chapter, we will use the variant data type to create an array of arrays. This makes it possible to create, and work with, data structures that would otherwise be impossible. It also allows one to operate on an entire row of an array. 

With this background, it can be seen why the Variant data type was used in the prior example when it was desired to assign an entire array to a variable. 

According to Parthe et al. (1993), a standardization procedure is necessary in the presentation of the relevant data characteristic of a crystal structure (see also Parthe and Gelato 1984). A convenient description of the structure types is then possible using the Wyckoff sequence (the letters of the occupied Wyckoff sites). This allows a finer classification of structure types and offers suggestions not only for recognizing isotypic structures but also possible structural relationships like substitution, formation of vacancy or filled-in structure variants. 

From the above discussion it follows that all types, variants or schemes of the cross-validation type by necessity must be inferior, indeed unscientific [27,28], precisely because no TSE-contributions from any future data set is ever validated. Only test set validation stands up to the logical demands of the validation imperative itself. Cross-validation is therefore logically and scientifically discredited and must never be used as a replacement for a true test (f cross-validation is used, this must always be accompanied by appropriate warnings [27,28]. 

Evaluation of the contribution made by the proximal ligand to the oxidation-reduction equilibrium of Mb (H93 in the wild-type protein (Fig. 2)) has been more difficult because substitution of the proximal residue results in expression of apo-Mb without heme incorporation. All of the available data for these variants (Table I), therefore, derive from proteins prepared by reconstitution of purified recombinant apoprotein with exogenous heme 69, 70, 72). In those cases where trace quantities of native Mb are produced (73), heme extraction followed by reconstitution was undertaken to eliminate complications from suIfMb... 

The conversion of the kinetic data into AAG -values (Table 4.2) assumes that the rate-limiting step is the same in wild type and variant. It also assumes that the mutation does not cause structural rearrangements. Only in very few cases have the kinetic studies on the transition state stabilization by the oxyanion hole contributions been complemented by protein crystallographic studies of the liganded wild-type and mutated variant. One such example, discussed in more detail below, concerns the studies on the Ser42Ala variant of cutinase, in which case it was found that the structural changes are minimal [19]. 

The relaxation data in Fig. 12 show that the only region of significant internal mobility in either the wild-type or variant protein is at the N-terminus. Note the sign difference for the different heteronuclear X- H NOEs, with an increased mobility leading to an increase in NOE for 13C and a decrease for 15N... 

A question of particular interest concerns the catalytic advantage that a selenol in the active site of an enzyme has in comparison to a thiol group. It has been approached by replacing the selenocysteine in the formate dehydrogenase Ft by a cysteine residue and by determining the catalytic parameters of the Se-wild-type species with the mutant S-species. Table 1 presents the data obtained. They show that koit of the Se enzyme is more than 300-fold higher than that of the S variant and that the affinity to the substrate is only marginally affected. Similar replacements of selenocysteine by cysteine in other enzymes like the deiodinase type 1 or methionine sulfoxide reductase B corroborated these results. 

The optional Lower To can be omitted. Type can be Integer, Single, Double, Variant, etc. See the complete list of data types in "VBA Data Types" in chapter 13.) A Variant array can hold values of different data types (e.g., 1.173 and "Billo, E. Joseph"). 

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