# Mean Deviation Over Period

## Technical Analysis Indicator: md ## Function Prototype

/* Mean Deviation Over Period */
/* Type: math */
/* Input arrays: 1    Options: 1    Output arrays: 1 */
/* Inputs: real */
/* Options: period */
/* Outputs: md */
int ti_md_start(TI_REAL const *options);
int ti_md(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 Mean Deviation Over Period indicator calculates the absolute mean deviation over a period.

It takes one parameter: the period n.

The calculation is as follows:

$$ma_{t} = \frac{1}{n} \sum_{i=0}^{n-1} in_{t-i}$$
$$md_{t} = \frac{1}{n} \sum_{i=0}^{n-1} | in_{t-i} - ma_{t} |$$

## Example Usage

### Calling From C

/* Example usage of Mean Deviation Over Period */
/* Assuming that 'input' is a pre-loaded array of size 'in_size'. */
TI_REAL *inputs[] = {input};
TI_REAL options[] = {5}; /* period */
TI_REAL *outputs; /* md */

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

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

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


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

-- Example usage of Mean Deviation Over Period
md = ti.md(input, 5)


## Example Calculation

period = 5

dateinputmd
2005-11-0181.59
2005-11-0281.06
2005-11-0382.87
2005-11-0483.00
2005-11-0783.610.88
2005-11-0883.150.67
2005-11-0982.840.23
2005-11-1083.990.39
2005-11-1184.550.51
2005-11-1484.360.63
2005-11-1585.530.67
2005-11-1686.540.83
2005-11-1786.890.91
2005-11-1887.771.02
2005-11-2187.290.62

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