# Replace missing values from normal distribution

# 1 General

**Type:**- Matrix Processing**Heading:**- Imputation**Source code:**ReplaceMissingFromGaussian.cs

# 2 Brief description

Missing values will be replaced by random numbers that are drawn from a normal distribution. The parameters of this distribution can be optimized to simulate a typical abundance region that the missing values would have if they had been measured. In the absence of any a priori knowledge, the distribution of random numbers should be similar to the valid values. Often, missing values represent low abundance measurements. The default values are chosen to mimic this case.

# 3 Parameters

## 3.1 Width

Defines the width of the Gaussian distribution relative to the standard deviation of measured values (default: 0.3). A value of 0.5 would mean that the width of the distribution used for drawing random numbers is half of the standard deviation of the data.

## 3.2 Down shift

Specifies the amount by which the distribution used for the random numbers is shifted downwards (default: 1.8). This is in units of the standard deviation of the valid data.

## 3.3 Mode

Specifies whether the replacement of missing values should be applied to each expression column separately (default) or on the whole matrix at once (“Total matrix”).

## 3.4 Columns

Selected expression columns, where missing values should be replaced (default: all expression columns are selected).