How to set different sizes for plots in the same block with knitr?

I'm trying to create a html with markdown. I want to include several plots using a for loop like this:

```{r plotofnas, echo=FALSE, fig.width=2, message=FALSE, warning=FALSE}
for (i in list) { 
  barplot(i)
  plot(i)
}

The problem is that I want different sizes for the first and the second plot in the loop, specifically, I want the barplot to have a smaller width than the other plot. Looking for a solution I came across the fig.width option, but this will change the size of all of my plots, not only the barplots. Is there a possibility to only change the size of specific plots in one block in markdown?