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+# Calculate a time weighted average concentration
+
+The moving average is built only using the values in the past, so the
+earliest possible time for the maximum in the time series returned is
+after one window has passed.
+
+## Usage
+
+``` r
+twa(x, window = 21)
+
+# S3 method for class 'one_box'
+twa(x, window = 21)
+```
+
+## Arguments
+
+- x:
+
+  An object of type
+  [one_box](https://pkgdown.jrwb.de/pfm/reference/one_box.md)
+
+- window:
+
+  The size of the moving window
+
+## See also
+
+[`max_twa`](https://pkgdown.jrwb.de/pfm/reference/max_twa.md)
+
+## Examples
+
+``` r
+pred <- sawtooth(one_box(10),
+  applications = data.frame(time = c(0, 7), amount = c(1, 1)))
+max_twa(pred)
+#> $max
+#>    parent 
+#> 0.9537545 
+#> 
+#> $window_start
+#> parent 
+#>      0 
+#> 
+#> $window_end
+#> parent 
+#>     21 
+#> 
+```