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31.4 Variable naming

The recommended variable naming is to follow C/C++ naming conventions, in which variables are lowercase, with the underscore character (_) used as a separator. Thus it is preferred to use sigma_y, rather than the run together sigmay, camel-case sigmaY, or capitalized camel-case SigmaY. Even matrix variables should be lowercased.

The exception to the lowercasing recommendation, which also follows the C/C++ conventions, is for size constants, for which the recommended form is a single uppercase letter. The reason for this is that it allows the loop variables to match. So loops over the indices of an \(M \times N\) matrix \(a\) would look as follows.

for (m in 1:M)
  for (n in 1:N)
     a[m,n] = ...