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.
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 totobut 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.
Examples
res <- breaks_ppm(20, 50, by = 1, ppm = 50)
res
#> [1] 20.00000 21.00105 22.00215 23.00330 24.00450 25.00575 26.00705 27.00840
#> [9] 28.00980 29.01125 30.01275 31.01430 32.01590 33.01755 34.01926 35.02101
#> [17] 36.02281 37.02466 38.02656 39.02851 40.03051 41.03256 42.03467 43.03682
#> [25] 44.03902 45.04127 46.04357 47.04593 48.04833 49.05078 50.05328
## difference between the values increases (by ppm)
diff(res)
#> [1] 1.001050 1.001100 1.001150 1.001200 1.001250 1.001300 1.001350 1.001400
#> [9] 1.001450 1.001501 1.001551 1.001601 1.001651 1.001701 1.001751 1.001801
#> [17] 1.001851 1.001901 1.001951 1.002001 1.002052 1.002102 1.002152 1.002202
#> [25] 1.002252 1.002302 1.002352 1.002402 1.002452 1.002503