# Vector Subtraction

## Function Prototype

/* Vector Subtraction */
/* Type: simple */
/* Input arrays: 2    Options: 0    Output arrays: 1 */
/* Inputs: real, real */
/* Options: none */
/* Outputs: sub */
int ti_sub_start(TI_REAL const *options);
int ti_sub(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.

Sub simply takes two input arrays and returns their difference.

$$sub_{t} = a_{t} - b_{t}$$

This is sometimes useful as a building block to more complex functions.

## Example Usage

### Calling From C

/* Example usage of Vector Subtraction */
/* Assuming that 'input1' and 'input2' are pre-loaded arrays of size 'in_size'. */
TI_REAL *inputs[] = {input1, input2};
TI_REAL options[] = {}; /* No options */
TI_REAL *outputs[1]; /* sub */

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

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

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


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

-- Example usage of Vector Subtraction
sub = ti.sub(input1, input2)


## Example Calculation

dateinputinput2sub
2005-11-0181.5981.85-0.26
2005-11-0281.0681.20-0.14
2005-11-0382.8781.551.32
2005-11-0483.0082.910.09
2005-11-0783.6183.100.51
2005-11-0883.1583.41-0.26
2005-11-0982.8482.710.13
2005-11-1083.9982.701.29
2005-11-1184.5584.200.35
2005-11-1484.3684.250.11
2005-11-1585.5384.031.50
2005-11-1686.5485.451.09
2005-11-1786.8986.180.71
2005-11-1887.7788.00-0.23
2005-11-2187.2987.60-0.31

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