xy_sprintf: Slightly adjusted version of sprintf
In LAJordanger/HVLstatistikk: HVL - simple shiny applications for teaching.

Slightly adjusted version of sprintf

1	xy_sprintf(.txt, x, ...)

`.txt`	A textstring to be included at the left side of the equality (or approximation) sign.
`x`	A number which will be included at the right side of the equality (or approximation) sign. Note that `x` will be converted to a text-string by the help of the function `xy_formatC`.
`...`	Arguments to be given to `xy_formatC`, which will govern how `x` is transformed into the text to be included at the right side of the equality (or approximation) sign.

This function will return a character-string that either states that .txt is equal to x, or that .txt is approximately equal to x. Depending on the arguments in ..., this text can then either be used to present the result in a ggplot or it can be included in the describing text.