The phrase "an approximation for calculating" is correct and usable in written English.
It can be used when discussing methods or formulas that provide a close estimate for a particular calculation or measurement.
Example: "The formula serves as an approximation for calculating the area of irregular shapes."
Alternatives: "an estimate for computing" or "a method for approximating".
Equation (1.3) with (alpha=1) is called a Chaplygin gas, which was introduced by Chaplygin [5] and Tsien [6] as a mathematical approximation for calculating the lifting force on a wing of an airplane in aerodynamics.
Their model creates an approximation method for calculating the degree of untruthfulness for reviews based on the duplicate identification results by estimating the overlap of semantic contents among reviews using a Semantic Language Model (SLM).
For each reporter ion peak range, the total area is calculated by summing the areas between ion peak pairs using the trapezoid approximation for calculating the area under a curve.
Finally, it follows that the projection approximation for calculating the phase shift must fail for strong phase shifts of higher than quadratic form.
Graphical method (GM) (Johnson 1978) uses Weibull cumulative distribution function and least square approximation for calculating the scale and shape parameters.
Finally, in this paper, the simple complex eikonal equations, in quasi-longitudinal (QL) approximation, for calculating the non-deviative absorption coefficient due to the propagation across the D-layer are encoded into a so called COMPLEIK (COMPLex EIKonal) subroutine of the IONORT (IONOspheric Ray-Tracing) program (Azzarone et al., 2012).
The other relies on a fast approximation procedure for calculating Poisson-binomial P-values, which we call bi-binomial approximation (BBA) or bi-binomial distribution (BBD).
Geometric considerations are taken into account when calculating an approximation for t i.
All analyses were conducted with Stata V.12, using the Taylor expansion approximation technique for calculating the design-based estimates of variance.
In comparison with the packages nlme and lme4 in R, the MIXED procedure in SAS provides also Satterthwaite and Kenward-Roger approximation methods for calculating the denominator df which especially result in some improvements in the resulting p-values.
