To fit psychometric functions using the logarithm of the independent variable, `log = TRUE`

should be added to `quickpsy`

. To illustrate it, we use the data from the classic experiment of Hecht, Shlaer and Pirenne (1942) that is included in the MPDiR package associated to the book of Knoblauch and Maloney (2012).

```
library(cowplot)
library(quickpsy)
library(MPDiR) #contains HSP
HSP <- HSP %>% mutate(k = round(N * p / 100)) # to calculate the number of 'yes'
fit <- quickpsy(HSP, Q, k, N, prob = .6, grouping = .(Run, Obs), log = T)
pa <- fit %>% plot(xpanel = Run, ypanel = Obs)
pb <- fit %>% plotpar()
pc <- fit %>% plotthresholds()
pbc <- plot_grid(pb, pc, ncol =1, labels = c('B', 'C'))
plot_grid(pa, pbc, labels = 'A')
```

## References

Knoblauch, K., & Maloney, L. T. (2012). Modeling Psychophysical Data in R. New York: Springer.

Hecht, S., Shlaer, S., Pirenne, M.H. (1942) Energy, quanta and vision. J. Gen. Physiol. 25, 819– 840.