r - Knitr to docx - Increasing max fig.width beyond 6 inches? -

i'm new knitr, rmarkdown , pandoc, , having trouble figuring out set options.

i'd have figure width wider 6 inches. in default word doc margins, seems there @ least 6.5 inches available, , there's more if willing reduce margins.

however, when try set fig.width in chunk creates word doc, graphs never more 6 inches wide. instead changes aspect ratio.

is there option somewhere overriding fig.width? can change in reference docx?

here's example .rmd.

--- title: "graph size test" output: word_document ---  # test 1   looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong string ```{r, echo = false, fig.width = 6, fig.height = 5}  df <- data.frame(x = c(1, 2, 3), y = c(1, 10, 3)) plot(df$x, df$y)  ```   ## test 2  looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong string ```{r, echo = false, fig.width = 6.5, fig.height = 5} plot(df$y, df$x) ```  ## test 3  still 6 inches wide, shorter. ```{r, echo = false, fig.width = 10, fig.height = 5} plot(df$y, df$x) ``` 

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edit:

to make matters worse, graphs being set 6 inches wide when document in landscape orientation. how can make them larger?