# poly4root: Roots of a Fourth Degree Polynomial In trio: Testing of SNPs and SNP Interactions in Case-Parent Trio Studies

## Description

While `poly4root` computes the (real-valued) roots of a polynomial of fourth degree, `poly4rootMat` can be applied to several polynomials of fourh degree at once by assuming that each row the input matrix contains the coefficients for one of the polynomials.

## Usage

 ```1 2 3``` ```poly4root(a) poly4rootMat(amat) ```

## Arguments

 `a` a numeric vector of length five specifying the coefficients of the polynomial `a[1]`*x^4 + `a[2]`*x^3 + `a[3]`*x^2 + `a[4]`*x + a[5]. `amat` a numeric matrix with five columns in which each row contains the five coefficients of a polynomial of fourth degree.

## Value

For `poly4root`, a vector containing the real-valued roots of the polynomial. For `poly4rootMat`, a matrix with four columns in which each row contains the real-valued roots of the corresponding polynomial. If a polynomial has less than four real-valued roots, the remaining entries in the corresponding row are set to `NA`.

## Author(s)

Holger Schwender, holger.schwender@udo.edu

## Examples

 ```1 2 3 4``` ```# The roots of # 2 * x^4 + 3 * x^3 - x^2 + 5 * x^1 - 4 # can be determined by poly4root(c(2, 3, -1, 5, -4)) ```

### Example output

```[1] -2.3318945  0.6491345
Warning message:
In sqrt(tmp) : NaNs produced
```

trio documentation built on Nov. 8, 2020, 7:41 p.m.