# Average Directional Movement Index

## Function Prototype

/* Average Directional Movement Index */
/* Type: indicator */
/* Input arrays: 3    Options: 1    Output arrays: 1 */
/* Inputs: high, low, close */
/* Options: period */
/* Outputs: dx */
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 Average Directional Movement Index can help determine trend strength.

It takes one option, the period n.

Given Directional Movement Index, calculation is as follows:

$$\text{adx}_{t} = \frac{n-1}{n} \text{adx}_{t-1} + \text{dx}_{t}$$

## Example Usage

### Calling From C

/* Example usage of Average Directional Movement Index */
/* Assuming that 'high', 'low', and 'close' are pre-loaded arrays of size 'in_size'. */
TI_REAL *inputs[] = {high, low, close};
TI_REAL options[] = {5}; /* period */
TI_REAL *outputs[1]; /* dx */

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

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

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


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

-- Example usage of Average Directional Movement Index
dx = ti.adx(high, low, close, 5)


## Example Calculation

period = 5

datehighlowclosedx
2005-11-0182.1581.2981.59
2005-11-0281.8980.6481.06
2005-11-0383.0381.3182.87
2005-11-0483.3082.6583.00
2005-11-0783.8583.0783.61
2005-11-0883.9083.1183.15
2005-11-0983.3382.4982.84
2005-11-1084.3082.3083.99
2005-11-1184.8484.1584.5541.38
2005-11-1485.0084.1184.3644.29
2005-11-1585.9084.0385.5349.42
2005-11-1686.5885.3986.5454.92
2005-11-1786.9885.7686.8959.99
2005-11-1888.0087.1787.7765.29
2005-11-2187.8787.0187.2967.36

## Other Indicators

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