etl/docs/maths/rms.md

---
title: "RMS (Root Mean Square)"
---

{{< callout type="info">}}
  Header: `rms.h`  
  Since: `20.9.0`  
{{< /callout >}}

```cpp
template <typename TInput, typename TCalc = TInput>
class rms : public etl::unary_function<TInput, void> 
```

`TInput` The input data type.  
`TCalc` The type to use for internal calculations. By default, equal to TInput.

---

```cpp
rms()
```
**Description**  
Default constructor.

---

```cpp
template <typename TIterator>
rms(TIterator first, TIterator last)
```
**Description**  
Construct from an iterator range.

---

```cpp
void add(TInput value1)
```
**Description**  
Add a value.

---

```cpp
template <typename TIterator>
void add(TIterator first, TIterator last)
```
**Description**  
Add a range of values.

---

```cpp
void operator()(TInput value)
```
**Description**  
Add a values.

---

```cpp
template <typename TIterator>
void operator()(TIterator first, TIterator last)
```
**Description**  
Add a range of values.

---

```cpp
double get_rms()
```
**Return**  
The calculated RMS for the data.

---

```cpp
operator double()
```
**Return**  
The calculated RMS value for the data.

---

```cpp
size_t count() const
```
**Description**  
Get the total number added entries.

---

```cpp
void clear()
```
Clear the mean.

## Example
```cpp
std::array<char, 10> input
{
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9
};

etl::rms<char, int32_t> rms(input.begin(), input.end());

double rms_result;

rms_result = rms; // rms_result  == 5.21
```