# Technical Studies Reference

### Percent Change Since Previous Close

The study calculates and displays the Percent Change Since Previous Close of the data specified by the Input Data Input.

Let $$X$$ be a random variable denoting the Input Data, and let $$X_t$$ be its value at Index $$t$$, and let $$v$$ be the Multiplier Input. The Percent Change Since Previous Close at Index $$t$$ is denoted as $$\%\Delta X^{(PC)}_t$$, and we compute it as follows.

For Historical Charts:

$$\%\Delta X^{(PC)}_t(v) = v\cdot\frac{X_t - X_{t - 1}}{X_{t - 1}}$$

$$\%\Delta X^{(PC)}_t(v) = v\cdot\frac{X_t - X_{t_{start}}}{X_{t_{start}}}$$

Note: This formula only give a true Percent Change if the Multiplier Input is set to $$100$$.

$$t_{start}$$ is determined as follows.

• For the first day in the chart, $$t_{start} = 0$$, which is the Index of the first bar in the chart.
• For the first bar in each subsequent day in the chart, $$t_{start}$$ is the Index of the final bar of the previous day in the chart.

More detailed information about how the time of the Closing bar of the previous trading day is determined can be found in the section on Session Times.