Hi Plotly community!

I run into unexpected behaviors when using Plotly to produce interactive matrices through the *ggplotly* function to imitate the results of *ggplot2*’s *geom_raster* method.

A simple and reproducible example is as follows:

```
library(ggplot2)
library(plotly)
dataset = data.frame(A = runif(20), B = factor(sample(1:10, 20, replace = T)), C = factor(sample(1:10, 20, replace = T)))
gp = ggplot(dataset, aes(x = B, y = C, fill = A)) + geom_raster()
ggplotly(gp)
gp
```

Here I want to display a matrix showing occurrences of

a factor B against a factor C, and color it by the value A.

The ggplot version of the matrix, as stored in the *gp* variable, corresponds to what is in the *dataset* matrix and what I expect. However some points (but not all) are shifted in the plotly version of the matrix, and their position does not correspond to their actual B and C coordinates. This is shown on the next figure, where the tooltip describes a point of coordinates (B = 2, C = 7), present in the dataset, but displayed at the coordinates (B = 3, C = 7).

Is this difference between the ggplot behavior and the ggplotly equivalent a bug or am I missing anything?

Thanks for your help!

PS: I used R 3.4.1, plotly_4.7.1 and ggplot2_2.2.1.9000.