The documentation of val() says, in the second section for val(val):

"Checks, or selects, all the radio buttons, checkboxes, and select options that match the set of values."

And the example code shows that it works given a single non-Array value to select the option on a non-multiple select:

$("#single").val("Single2");

But this does not work for radio or checkbox inputs. Given this HTML:

<input type="radio" name="ordinal" value="1">First</input>

<input type="radio" name="ordinal" value="2">Second</input>

code like this:

$("[@name='ordinal']").val("2");

surprisingly ends up setting the "value" attribute of all the radio buttons to "2" like this:

<input type="radio" name="ordinal" value="2">First</input>

<input type="radio" name="ordinal" value="2">Second</input>

instead of setting the "checked" attribute on the radio button with value "2" as expected, like this:

<input type="radio" name="ordinal" value="1">First</input>

<input type="radio" name="ordinal" value="2" checked>Second</input>

Patch to provide the expected (and in my opinion documented) behavior attached.