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# Calculate Trace of a Matrix in R Programming – tr() Function

• Last Updated : 19 Jun, 2020

`tr()` function in R Language is used to calculate the trace of a matrix. Trace of a matrix is the sum of the values on the main diagonal(upper left to lower right) of the matrix.

Syntax: tr(x)

Parameters:
x: Matrix

Example 1:

 `# R program to calculate``# trace of a matrix`` ` `# Loading library``library(psych)`` ` `# Creating a matrix``A ``=` `matrix( ``  ``c(``6``, ``1``, ``1``, ``4``, ``-``2``, ``5``, ``2``, ``8``, ``7``),  ``  ``nrow ``=` `3``,              ``  ``ncol ``=` `3``,              ``  ``byrow ``=` `TRUE           ``) `` ` `A`` ` `# Calling tr() function``cat(``"Trace of A:\n"``) ``tr(A)`

Output:

```     [, 1] [, 2] [, 3]
[1, ]    6    1    1
[2, ]    4   -2    5
[3, ]    2    8    7
Trace of A:
[1] 11
```

Example 2:

 `# R program to calculate``# trace of a matrix`` ` `# Loading library``library(psych)`` ` `# Creating a matrix``A ``=` `matrix(c(``1``:``9``), ``3``, ``3``) `` ` `A`` ` `# Calling tr() function``cat(``"Trace of A:\n"``) ``tr(A)`

Output:

```     [, 1] [, 2] [, 3]
[1, ]    1    4    7
[2, ]    2    5    8
[3, ]    3    6    9
Trace of A:
[1] 15
```

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