# Rate of Change

## Function Prototype

/* Rate of Change */
/* Type: indicator */
/* Input arrays: 1    Options: 1    Output arrays: 1 */
/* Inputs: real */
/* Options: period */
/* Outputs: roc */
int ti_roc_start(TI_REAL const *options);
int ti_roc(int size,
TI_REAL const *const *inputs,
TI_REAL const *options,
TI_REAL *const *outputs);

## Description

This documentation is still a work in progress. It has omissions, and it probably has errors too. If you see any issues, or have any general feedback, please get in touch.

The Rate of Change indicator calculates the change between the current price and the price n bars ago.

It takes one parameter, the period n.

The calculation is as follows:

$$roc_{t} = \frac{in_{t}-in_{t-n}}{in_{t-n}}$$

## Example Usage

### Calling From C

/* Example usage of Rate of Change */
/* Assuming that 'input' is a pre-loaded array of size 'in_size'. */
TI_REAL *inputs[] = {input};
TI_REAL options[] = {5}; /* period */
TI_REAL *outputs[1]; /* roc */

/* Determine how large the output size is for our options. */
const int out_size = in_size - ti_roc_start(options);

/* Allocate memory for output. */
outputs[0] = malloc(sizeof(TI_REAL) * out_size); assert(outputs[0] != 0); /* roc */

/* Run the actual calculation. */
const int ret = ti_roc(in_size, inputs, options, outputs);
assert(ret == TI_OKAY);


### Calling From Lua (with Tulip Chart bindings)

-- Example usage of Rate of Change
roc = ti.roc(input, 5)


## Example Calculation

period = 5

dateinputroc
2005-11-0181.59
2005-11-0281.06
2005-11-0382.87
2005-11-0483.00
2005-11-0783.61
2005-11-0883.150.02
2005-11-0982.840.02
2005-11-1083.990.01
2005-11-1184.550.02
2005-11-1484.360.01
2005-11-1585.530.03
2005-11-1686.540.05
2005-11-1786.890.04
2005-11-1887.770.04
2005-11-2187.290.04

## Other Indicators

Previous indicator: Qstick

Next indicator: Rate of Change Ratio

Random indicator: Vector Multiplication