The short is answer is no, you can't filter charts.

The longer answer is yes, you can filter charts.  But, it requires thinking about the entire solution a little differently.

Let's suppose you have four data types, typeA, typeB, typeC, and typeD.  Now, your report includes all four types, so you don't want to filter the report as a whole with Select criteria.  And, you've grouped the data based on some other field, so you can't just plop the reports in the group header.  How do you create a chart just for typeA?

Create a formula, like so:

If {MyDataType} = "typeA" Then 1 Else 0

Now, if you want a count of the records that are "typeA", you just sum up this formula, instead of doing a count.

Ah, but suppose you want to total up some other value for your "typeA" records.  Well, it's the same process:

If {MyDataType} = "typeA" Then {MyOtherValue} Else 0

I have used this method to do some fairly sophisticated data shaping for my charts (I produce metrics charts in Crystal as my job).  One interesting caveat, though, is that it does produce a lot of zero values.  These are often easy to filter out if you are using Top N or specified sort charts.  They are pretty much always going to fall into that "Other" category.  And, of course, a zero value is generally invisible on a chart.  But, it can have some unexpected data points show up in your legend.

Generally speaking, no.  You can't really do conditional formatting inside a chart.

I'm assuming you looked at the Top N and "specified order" options?

What kind of chart are you using?