|
|  |
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]
Re: st: Mata subscripts on the left of an assignment
Hello Statalisters!
Not exactly to the topic, but hopefully close enough to avoid starting a new
thread.
Can anybody clarify why can't I use subscripts after a call to e(something)?
Example:
---------------------------------
. mat l e(b)
e(b)[1,2]
bywibs _cons
y1 -.70162747 38.106444
. mat A=e(b)[1,1]
invalid syntax
r(198);
. mat B=e(b)
. mat A=B[1,1]
. mat l A
symmetric A[1,1]
c1
r1 -.70162747
---------------------------------
This is definitely not a bug, since intuitively e( ) is a function, but why
such a behaviour with subscripts is not supported?
Is there a shorter way to extract a vector, etc from the estimates without
using a temporary matrix? (in this example matrix B).
Regards,
Sergiy
----- Original Message -----
From: "Ben Jann" <[email protected]>
To: <[email protected]>
Sent: Wednesday, February 28, 2007 10:29 PM
Subject: Re: st: Mata subscripts on the left of an assignment
Cool. I stumbled over that too some time ago and thought I was just
too stupid to understand it.
ben
On 2/28/07, William Gould, Stata <[email protected]> wrote:
Tom Palmer <[email protected]> ended a long posting with,
> Is Mata behaving incorrectly in code example 2 or is this my
> misunderstanding?
Mata is misbehaving in example 2. I have just listed the problem as a
bug.
Where the bug lies, however, may not be where Tom expects.
Example 2 in Tom's posting was
: y = (7\1\6\5)
: p = order(y,1)
: y = y[p]
: y[p] = y
: y
y should return unchanged, but it doesn't. Tom starts with
(7\1\6\5) and ends up with (1\1\6\1). The line that caused
the problem was
: y[p] = y
Tom asked, "Is Mata (incorrectly?) processing subscripts on the left of
an
assignment on an element by element basis"?
No. The LHS y[p] logic is fine. The problem is that y appeared on
the RHS of the assignment, too, and as Mata executed the y[p] from y,
the RHS changed as Mata filled in the left. As a demonstration,
substitute for the following
-----------------------------------------------
y[p] = y x = y
y[p] = x
-----------------------------------------------
The substitution will work, yet both should be equivalent.
We will fix Mata so that y[p]=y works.
-- Bill
[email protected]
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
