I suddenly realized just now that the line breaks for `LaTeX`

code in Rd files are also `\cr`

instead of `\\`

(which I thought to be in the past). `R CMD check`

will replace your `\cr`

with `\\`

when producing `LaTeX`

documentation files. If you write `\\`

directly in Rd files, it will be recognized as “*an escape character* + *a backslash*”, which surely is not a line break symbol.

I found such a problem in the documentation file for the function `brownian.motion()`

in my package animation. The original code is:

```
\deqn{x_{k + 1} = x_{k} + rnorm(1)\\
y_{k + 1} = y_{k} + rnorm(1)}
{x[k + 1] = x[k] + rnorm(1)\cr y[k + 1] = y[k] + rnorm(1)}
```

And actually it should be:

```
\deqn{x_{k + 1} = x_{k} + rnorm(1)\cr
y_{k + 1} = y_{k} + rnorm(1)}
{x[k + 1] = x[k] + rnorm(1)\cr y[k + 1] = y[k] + rnorm(1)}
```

I was just to write an email for help but I understood the reason for my problem (by checking the result from `R CMD check`

) before I sent my email.