## Tutorials

New tutorials that reflect the updated GeoFRED user interface are currently under development. If you would like to view older tutorials that vary from the current interface, you can do so by visiting the old tutorial site.

## Units Formulas

The following formulas are used to transform units:

**Change**

x(t) - x(t-1)

**Change from Year Ago**

x(t) - x(t-n_obs_per_yr)

**Percent Change**

((x(t)/x(t-1)) - 1) * 100

**Percent Change from Year Ago**

((x(t)/x(t-n_obs_per_yr)) - 1) * 100

**Compounded Annual Rate of Change**

(((x(t)/x(t-1)) ** (n_obs_per_yr)) - 1) * 100

**Continuously Compounded Rate of Change**

(ln(x(t)) - ln(x(t-1))) * 100

**Continuously Compounded Annual Rate of Change**

((ln(x(t)) - ln(x(t-1))) * 100) * n_obs_per_yr

**Natural Log**

ln(x(t))

**Notes:**

'x(t)' is the value of series x at time period t.

'n_obs_per_yr' is the number of observations per year. The number of observations per year differs by frequency:

Frequency | Observations per Year |
---|---|

Daily | 260 (no values on weekends) |

Annual | 1 |

Monthly | 12 |

Quarterly | 4 |

Bi-Weekly | 26 |

Weekly | 52 |

'ln' represents the natural logarithm.

'**' represents to the power of.