findFirstFeature: Feature matrix feature locator.

In ychen-uoft/msFeatureCmp: Mass Spectrometry Feature Comparator

Description

Finds the first feature in a feature matrix that has its specified element at a given key equal to a given target. If no feature satisfies the requirement, counts how many features have, at the same key, an element strictly less than the target (its rank in the matrix).

Usage

findFirstFeature(sortedFeatureMatrix, key = RT_IDX, target = 0)

Arguments

sortedFeatureMatrix	The sorted feature matrix to search.
key	The column in the matrix to search in.
target	The target value to search for, as a number.

Details

This function uses binary search to find the feature, so the feature matrix must be sorted ascending in the key column. Otherwise there is no guarantee that the search will yield the correct result.

Value

The index of the first feature that has its element at the given key equal to the given target, if it exists; the feature's rank otherwise.

Examples

## Not run: 
m <- matrix(1:10, nrow = 5, ncol = 2)
m[2, 1] <- 3
m[4, 1] <- 3
rank <- findFirstFeature(m, key = 1, target = 3)
rank  # Returns 2

## End(Not run)

ychen-uoft/msFeatureCmp documentation built on Dec. 23, 2021, 7:17 p.m.