transform.value.text: Format a single numerical value for a transformation text...

In freesurferformats: Read and Write 'FreeSurfer' Neuroimaging File Formats

Format a single numerical value for a transformation text file.

Description

17 significant decimal digits identify a double uniquely, so writing that many of them and reading them back preserves the value exactly – but only if the decimal conversion of the C library rounds correctly, and that is not true on every platform: on macOS (ARM64) the round trip of a value like -1e-7 / 7 loses one unit in the last place, because the value that is written is one digit off. The round trip is therefore verified here with R's own decimal conversion, and the number of digits is increased until the value survives it. The output therefore has no more digits than the platform can handle correctly, and it is guaranteed to be read back exactly by the same platform.

Usage

## S3 method for class 'value.text'
transform(value)

Arguments

value

single numerical value, the value to format.

Value

character string, the text representation of the value.

freesurferformats documentation built on Sept. 25, 2026, 1:07 a.m.