# Mass Index

## Technical Analysis Indicator: mass ## Function Prototype

/* Mass Index */
/* Type: indicator */
/* Input arrays: 2    Options: 1    Output arrays: 1 */
/* Inputs: high, low */
/* Options: period */
/* Outputs: mass */
int ti_mass_start(TI_REAL const *options);
int ti_mass(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 Mass Index is used to identify trend reversals.

Mass Index takes on parameter, the period n.

It is calculated for each bar as follows:

$$e_{t} = \frac{ema(high - low)}{ema(ema(high-low))}$$
$$mass_{t} = \sum_{i=0}^{n-1} e_{t-i}$$

The Exponential Moving Average used in the calculation each use a fixed period of 9.

## Example Usage

### Calling From C

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

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

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

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


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

-- Example usage of Mass Index
mass = ti.mass(high, low, 5)


## Example Calculation

period = 5

datehighlowmass
2005-11-0182.1581.29
2005-11-0281.8980.64
2005-11-0383.0381.31
2005-11-0483.3082.65
2005-11-0783.8583.07
2005-11-0883.9083.11
2005-11-0983.3382.49
2005-11-1084.3082.30
2005-11-1184.8484.15
2005-11-1485.0084.11
2005-11-1585.9084.03
2005-11-1686.5885.39
2005-11-1786.9885.76
2005-11-1888.0087.17
2005-11-2187.8787.01

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