## tcorr()

`tcorr (expr1, expr2, tdim1, tdim2)`

This function produces a spatial map of temporal correlation coefficients.

`expr1` - a valid GrADS expression that varies in time
`expr2` - a valid GrADS expression that varies in time and may also vary in X and Y
`tdim1` - starting time dimension expression
`tdim2` - ending time dimension expression

The `expr1` time series is correlated to the time series at each grid point in `expr2`. The result is a grid of correlation coefficients that matches the X and Y dimensions of `expr2`.

### Usage Notes

1. If both `expr1` and `expr2` vary only in time, the output is a single value.

2. Use the `scorr` function to do correlation over the spatial domain.

### Example

1. This example calculates the temporal correlation between sea level pressure and the defined variable elnino, an areal average of surface temperature in the equatorial Pacific.

       set x 1
       set y 1
       set z 1
       set t 1 100
       define elnino = aave(ts,lon=-160,lon=-80,lat=-10,lat=10)
       set lon -180 180
       set lat -90 90
       set z 1
       set t 1
       d tcorr(elnino, slp, t=1, t=100)