Your approach of using 'seconds' to describe your design is exactly
right, and it doesn't matter at all if your blocks are integer multiples
The design you describe doesn't seem to have any 'off' conditions. Your
onset array starts at 5.05, and 25.03, and 45.8, but the length of the
block (20.16) extends the entire distance from one onset to the next.
The duration should be the duration of the 'on' condition only.
All the best!
On Thu, 2009-03-05 at 15:49 +0000, SUBSCRIBE SPM Anonymous wrote:
> Dear all,
> I have a question about setting up design matrix for block length that is
> not a dividable by TR.
> I found out in older messages that one can set non-integer scan
> numbers/onset time in SPM5.
> I tried to use the onset time for my block.
> unit: second.
> onset: [5.05 25.03 45.8 .....]
> duration: 20.16
> and it turns out that my design matrix looks like this ( .jpg in attachment )
> I couldn't figure out why it is the case.
> This is just a 6-block block design, starting with a off-condition.