breaks_ppm: Sequence with increasing difference between elements

In rformassspectrometry/MsCoreUtils: Core Utils for Mass Spectrometry Data

Sequence with increasing difference between elements

Description

breaks_ppm creates a sequence of numbers with increasing differences between them. Parameter ppm defines the amount by which the difference between values increases. The value for an element i+1 is calculated by adding size to the value of element i and in addition also the ppm(a, ppm), where a is the value of the element i plus size. This iterative calculation is stopped once the value of an element is larger than to. The last value in the result vector will thus not be equal to to (which is in contrast to the base seq() function) but slightly higher.

A typical use case of this function would be to calculate breaks for the binning of m/z values of mass spectra. This function allows to create m/z-relative bin sizes which better represents measurement errors observed on certain mass spectrometry instruments.

Usage

breaks_ppm(from = 1, to = 1, by = 1, ppm = 0)

Arguments

from	numeric(1) with the value from which the sequence should start.
to	numeric(1) defining the upper bound of the sequence. Note that the last value of the result will not be equal to to but equal to the first number in the sequence which is larger than this value.
by	numeric(1) defining the constant part of the difference by which numbers should increase.
ppm	numeric(1) defining the variable part of the difference by which numbers should increase (expressed in parts-per-million of the values).

Value

numeric with the sequence of values with increasing differences. The returned values include from and to.

Author(s)

Johannes Rainer

Examples

res <- breaks_ppm(20, 50, by = 1, ppm = 50)
res

## difference between the values increases (by ppm)
diff(res)

rformassspectrometry/MsCoreUtils documentation built on Oct. 24, 2024, 1:52 p.m.