Free42 with Matrix Exponential
12-24-2021, 01:21 PM
Post: #1
 Akira Yamada Junior Member Posts: 2 Joined: Oct 2019
Free42 with Matrix Exponential
Hi,

Free42 seems to accept square matrix for the e^x function, but returns wrong results.

For example, make a matrix [2x2 matrix] with {{0,0},{0,0}} and press e^x.
The correct result must be {{1,0},{0,1}}, Free42 returns {{1,1},{1,1}}.
Next example, input {{0, pi},{-pi,0}} and e^x.
The correct result is {{-1,0},{0,-1}}, Free42 gets {{1,e^pi},{e^-pi,1}}.
Next example, input [3x3 matrix] with {{0,0,0},{0,0,0},{0,0,0}} and e^x.
The correct result is {{1,0,0},{0,1,0},{0,0,1}}, Free42 returns {{1,1,1},{1,1,1},{1,1,1}}.

Is this a bug? or am I operating it in a wrong way?

I am using Free42 3.0.8 and DM42 (DMCP 3.22, DM42 3.20, Free42 3.0.5).

Akira
12-24-2021, 02:26 PM
Post: #2
 Thomas Okken Senior Member Posts: 1,893 Joined: Feb 2014
RE: Free42 with Matrix Exponential
Like the HP-42S, Free42 applies unary functions to matrices element-wise, so the results you cite are as expected. If a true matrix exponential is desired, it would have to be implemented in user code, or added as a new, separate function.
12-24-2021, 11:56 PM
Post: #3
 Akira Yamada Junior Member Posts: 2 Joined: Oct 2019
RE: Free42 with Matrix Exponential
I see. I was so naive. Thanks for your trouble.

Akira

(12-24-2021 02:26 PM)Thomas Okken Wrote:  Like the HP-42S, Free42 applies unary functions to matrices element-wise, so the results you cite are as expected. If a true matrix exponential is desired, it would have to be implemented in user code, or added as a new, separate function.
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