Re: It's my turn! Message #19 Posted by Rodger Rosenbaum on 8 Apr 2006, 6:30 p.m., in response to message #18 by Werner
All of this discussion will be for the HP49, except where otherwise noted.
Well, the problem is the type 29/3 bug. I had thought this might be the problem when you first posted about it, and I checked the type of the matrix and it was 3. But when I checked the checksum, it was wrong. Looking carefully at the matrix, I noticed that some of the entries didn't have a decimal point, such as the {2 1} entry. Examining it further, I found that all the numbers that were single digit had no decimal point (except the single digit numbers that had a decimal in front, such as .1). Obviously, the calculator had been in exact mode when I typed in the matrix, and I didn't type a decimal point for the single digit numbers like the 4 in the {2 1} position.
In spite of the presence of these apparently "exact" integers, the type of the matrix is 3. To try to find out what's happening, I typed in a small matrix, [[1 2.][3. 4.]], and checked its type; the type was 29. Some more testing seemed to indicate that if a single element of an otherwise approximate matrix is exact, then the type of the matrix is 29. So why is my matrix type 3 when there are several "exact" elements?
Next, I put the matrix on the stack and executed ->ROW and checked the type of each row. The type of the individual rows was type 29(!}, except row 2, for which the type was 3. I then decomposed the matrix with ->COL and checked the type of the columns. They were all 29 except for column 5.
I put the calculator into exact mode, and typed in the matrix all over again, without typing a decimal point for the single integer entries. This matrix also exhibited the behavior I described above.
So, the type of a matrix isn't always 29 if there are some "exact" elements in it (at least, not on my HP49}.
Some more testing (entering these objects with the calculator in exact mode), gave the following results:
Object Type
[[1. 2]] 29
[[11. 2]] 3
[[2 11.]] 29
[[1.][2]] 29
[[11.][2]] 3
[[2][11.]] 29
The HP49G+ gave none of this anomalous behavior. If a matrix contains even one exact element, the whole matrix is type 29.
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