Re: [Scilab-users] Is cond([]) 0 or 1 ? (bug 15579)
Le 27/05/2018 à 23:49, Rafael Guerra a écrit : You guys may have missed the paper sent before on the algebra of empty matrices by Carl de Boor (Emeritus Professor in Mathematics and Computer Science), so I am sending it again: https://pdfs.semanticscholar.org/0f3b/c36f19d5c6a761c19fbc3c4ebde2f31b0a10.pdf He argues that the condition number of the square empty matrix [] = 0 and its det([]) = 1 No no, i did not miss it. His argument is that norm([]) is 0: /Any norm of an empty matrix is zero, as the supremum of the empty set of nonnegative numbers. This implies that the condition number of the square empty matrix [] is 0./ This does not prevent asking to Philippe why he proposes 1, noticeably if he also considers that norm([])==0, or not. The De Boor argument "/as the supremum of the empty set of nonnegative numbers."/ is not clear to me./ /Is it clear for you? Would you have a second convergent independent reference? Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Is cond([]) 0 or 1 ? (bug 15579)
You guys may have missed the paper sent before on the algebra of empty matrices by Carl de Boor (Emeritus Professor in Mathematics and Computer Science), so I am sending it again: https://pdfs.semanticscholar.org/0f3b/c36f19d5c6a761c19fbc3c4ebde2f31b0a10.pdf He argues that the condition number of the square empty matrix [] = 0 and its det([]) = 1 Regards, Rafael -Original Message- From: users [mailto:users-boun...@lists.scilab.org] On Behalf Of philippe Sent: Sunday, May 27, 2018 11:24 PM To: users@lists.scilab.org Subject: Re: [Scilab-users] Is cond([]) 0 or 1 ? (bug 15579) Le 27/05/2018 à 19:51, Samuel Gougeon a écrit : > [...] > > Please let us know more about your proposal for 1 instead of 0. I can't say it now, the best value also depends on the compatibility of this value with others assigned to matrix functions with argument []. I would like to check it before, but with the example you mention 0 looks a better choice. Philippe ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Is cond([]) 0 or 1 ? (bug 15579)
Le 27/05/2018 à 19:51, Samuel Gougeon a écrit : > [...] > > Please let us know more about your proposal for 1 instead of 0. I can't say it now, the best value also depends on the compatibility of this value with others assigned to matrix functions with argument []. I would like to check it before, but with the example you mention 0 looks a better choice. Philippe ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Is cond([]) 0 or 1 ? (bug 15579)
Hello Philippe, Le 24/05/2018 à 23:20, philippe a écrit : Le 21/05/2018 à 15:46, Samuel Gougeon a écrit : There are at least two way to do it : * either keep *cond([])* to *1* and set all *cond([], p)* to 1 instead of 0 * or set *cond([])* to *0*. I don't see any clear reason enforcing a choice rather than the other. Do you? from a mathematical point of view the Condition number of a matrix A is defined by cond(A)=||A|| . ||A^(-1)|| its interest is that when solving A*x=y rounding errors on y (eps) are amplified to be cond(A)*eps. The optimal value of cond(A) is 1 (for identity matrix) so for me it looks natural that cond([])=1 . I must confess that, unless claiming that *norm([])***is NOT 0, i do not catch clearly the logical of your conclusion * /"The optimal value of cond(A) is 1 (for identity matrix) so for me it looks natural that cond([])=1"/ Indeed, cond([]) = norm([])*norm(inv([])) = 0*norm([]) = 0*0 = 0 By the way, according to the clear explanation you give about the meaning of the condition number, the value 0 is even more optimal: it says that small variations are not getting amplified, but killed. Please let us know more about your proposal for 1 instead of 0. Regards Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Le 26/05/2018 à 14:10, Samuel Gougeon a écrit : Le 25/05/2018 à 11:02, Samuel Gougeon a écrit : Hello, Le 25/05/2018 à 10:45, Clément David a écrit : Hi, Thanks for your experimental work on that topic. I guess we could merge the parser fix easily however the `!` usage to recall a previous command will remain problematic. This usage does not seem to be documented somewhere in the help page, maybe we could discard it. What's your opinion on that ? It is an historical and standard feature, used not only in Scilab language. Please see the entry http://bugzilla.scilab.org/10776 The only issue is that it is still undocumented. It could be described in the Console's page. "The only issue" : hmm, not really. Even if the missing documentation is the main one, IMO this (already) very handy feature could be improved in at least two ways: * when no match is found in the history, nothing happens. For people who does not know the feature (or who has forgotten that it is available), this could be easily puzzling and felt as a bug. => when no match is found, Scilab shall print a message "No match found in history" * A listbox listing matches could be displayed, to select the only entry searched for. This might be done in two ways : o either typing "!" + one char as the very first characters would enter a completion mode based on the history, with matches listed in a listbox as described hereabove o or this could be done only after validating with , or CTRL+space as for the feature completion (but here targeted to the history with the leading "!") If a completion mode is implemented, then the message "no match found in history" could be displayed in the listbox instead of in the console (note that the general feature completion triggered with CTRL+space displays nothing when no match is found). This request for improvements is now reported here: http://bugzilla.scilab.org/15592 ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Another two cents. Allowing a leading exclamation mark in variable names seems to be, IMHO, a bad idea because (1) most computer languages do not seem to allow it and (2) some when encountering it, will interpret as logical negation. Regards, Rafael From: users [mailto:users-boun...@lists.scilab.org] On Behalf Of Samuel Gougeon Sent: Sunday, May 27, 2018 5:14 PM To: Users mailing list for Scilab Subject: Re: [Scilab-users] Exclamation mark in variable names Le 27/05/2018 à 16:30, Wozai a écrit : Dear Samuel, my point is, it wasn't possible to execute "!A=1" in Scilab 5.x (without prepending a space) and IMHO one should really *improve* the situation in Scilab 6, rather than just restoring the status quo. Thank you Wozai for having confirmed my reading of your messages. What Jens and i see is that Scilab 6 has not kept a status quo: by removing "!" from allowed characters, and by not fixing this, Scilab 6 is downgraded now for almost 3 years it is released. Unfortunately, this is not a status quo. I definitively agree that improving Scilab is necessary. This is why i am involved in it. But i definitely disagree about the fact that what is considered as an improvement or a downgrade is the decision of one person or a very few people just declaring that "This is better than existing features. It must be changed!" (with a frequent trailing exclamation mark). Other users than you and me, more numerous than you alone, could easily consider that keeping the usage of "!" as the history call is preferable, because they use to use it in other environments, and then would consider this change as a regression, not an improvement. You seem to consider that using very occasionally a leading space to address a variable is really a big deal. But how many coders name preferably their variables with a leading "!" such that having to prepend a space actually becomes a big deal? I am sorry, but in all the external codes i had to work on for 20 years, variables with a leading "!" were rare enough that i don't remember having met a single one. The usual way to propose an improvement is to post a wish on Bugzilla. Yours is welcome! I let Clement pushing the fix for the parser, and i hope it will be straightforwardly merged. I will wait 2-3 weeks before documenting the history recall and CTRL+Space completion features in the Console page. If within this time it is decided to change for ":", the page won't have to be possibly updated afterwards. Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Le 27/05/2018 à 16:30, Wozai a écrit : Dear Samuel, my point is, it wasn't possible to execute "!A=1" in Scilab 5.x (without prepending a space) and IMHO one should really *improve* the situation in Scilab 6, rather than just restoring the status quo. Thank you Wozai for having confirmed my reading of your messages. What Jens and i see is that Scilab 6 has not kept a status quo: by removing "!" from allowed characters, and by not fixing this, Scilab 6 is downgraded now for almost 3 years it is released. Unfortunately, this is not a status quo. I definitively agree that improving Scilab is necessary. This is why i am involved in it. But i definitely disagree about the fact that what is considered as an improvement or a downgrade is the decision of one person or a very few people just declaring that "This is better than existing features. It must be changed!" (with a frequent trailing exclamation mark). Other users than you and me, more numerous than you alone, could easily consider that keeping the usage of "!" as the history call is preferable, because they use to use it in other environments, and then would consider this change as a *regression*, not an improvement. You seem to consider that using very occasionally a leading space to address a variable is really a big deal. But how many coders name preferably their variables with a leading "!" such that having to prepend a space actually becomes a big deal? I am sorry, but in all the external codes i had to work on for 20 years, variables with a leading "!" were rare enough that i don't remember having met a single one. The usual way to propose an improvement is to post a wish on Bugzilla. Yours is welcome! I let Clement pushing the fix for the parser, and i hope it will be straightforwardly merged. I will wait 2-3 weeks before documenting the history recall and CTRL+Space completion features in the Console page. If within this time it is decided to change for ":", the page won't have to be possibly updated afterwards. Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Dear Samuel, my point is, it wasn't possible to execute "!A=1" in Scilab 5.x (without prepending a space) and IMHO one should really *improve* the situation in Scilab 6, rather than just restoring the status quo. Cheers, Wozai -- Sent from: http://mailinglists.scilab.org/Scilab-users-Mailing-Lists-Archives-f2602246.html ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Le 27/05/2018 à 13:45, Wozai a écrit : Hi, In theory they are "completely independent", but currently as a matter of fact there is a clash wrt. to the semantics of the "!" character. Wozai, i am afraid i don't catch your point. Your point is not specifically about Scilab 6, is it? You already disagreed with Scilab 5 behavior about using "!" to recall the history, while "!" was actually accepted in identifiers, didn't you? If so, then, your point is clearly distinct from Jens (and any user using variable names including "!") urgent claim, that is specific to a Scilab 5 => 6 change. If "!" is reintroduced among allowed characters in identifiers -- including as the first one --, and "!" is not changed into ":" to recall the history, do we get with the fixed Scilab 6 anything else than the Scilab < 6 behavior? Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Simulating phase modulation
Hi Gary Thanks for your input. I went the analytic route for now, and simplified a bit (as you often do with analytic solutions). You're right that from an electro-mechanical point of view, superposition applies, but as the waves transmit in acoustics in air - not, I'm afraid, this is where we see the distortion, simply because the speaker cone moves several millimeter. Best regards, Claus On Sat, May 26, 2018 at 10:55 PM Gary Nelson wrote: > Claus, > > Back in the late 60s, I did my PhD research using analytic signal. Yes,it > works, and the implementation details are more complex that we find on the > link. A few years ago, I implemented a system for analyzing harbor porpoise > vocalizations using scilab. For example, instantaneous phase(t) wants to be > differentiable if instantaneous frequency is to be positive. I found that > octave bands are the widest that preserves this feature. Yes, you can > calculate phase(t) = atan(imaginary/real), but you have to add 2PI when > atan wraps around in order to make phase monotonically increase. > > > > Also, I am not convinced that a loudspeaker does phase modulation. > Certainly, if the speaker is linear, then superposition applies. If phase > modulation occurs, it is a non-linear effect. Perhaps that effect is real, > but we need to see a model to show how it comes to be. > > > > I might be able to help you write analytic signal code. > > > > Good wishes > > Gary Nelson > > > > > > Sent from my Windows 10 phone > > > > *From: *Claus Futtrup > *Sent: *Saturday, May 26, 2018 7:41 AM > *To: *International users mailing list for Scilab. > > *Subject: *Re: [Scilab-users] Simulating phase modulation > > > > Hi Rafael > > > > Thank you, I shall print and study. :-) > > > > Cheers, > > Claus > > > > On Fri, May 25, 2018 at 8:42 PM Rafael Guerra > wrote: > > Hi Claus, > > > > I am not aware of such function. However, you can find simple code here > below for both phase modulation and demodulation, which is straightforward > to translate in Scilab: > > > https://www.gaussianwaves.com/2017/06/phase-demodulation-using-hilbert-transform-application-of-analytic-signal/ > > > > Note that the phase modulation is coded differently from you snippet below. > > > > Regards, > > Rafael > > > > *From:* users [mailto:users-boun...@lists.scilab.org] *On Behalf Of *Claus > Futtrup > *Sent:* Friday, May 25, 2018 7:17 PM > *To:* International users mailing list for Scilab. > > *Subject:* [Scilab-users] Simulating phase modulation > > > > Hi there > > > > In a loudspeaker the driver can move several millimeter in an attempt to > reproduce a low-frequency note. If the speaker also at the same time > produce a higher tone, this second tone is phase modulated by the first > one. This is a distortion of the original signal which I'd like to simulate > / illustrate with some simple Scilab code, if possible. > > > > In Matlab this can be simulated with pmmod. > > https://matlabandsimulink.wordpress.com/2013/03/12/phase-modulation/ > > > > Is there a similar function in Scilab? (name - please ?) > > > > Here's the code I have written so far - this is the part that shows the > input signal (the un-distorted signal): > > > > sample_rate=2; > > t = 0:1/sample_rate:0.6; > > N=size(t,'*'); *//number of samples* > > y1 = sin(2*%pi*50*t); > > y2 = 0.5*sin(2*%pi*500*t); > > *// y2 = 0.5*sin(2*%pi*500*t+%pi/4);* > > s=y1+y2+grand(1,N,'nor',0,1); > > > > *// Plot time-domain* > > endplot = round(N/15); > > twoplots = scf(); *// Set Current Figure (Graphics Window)* > > subplot(211); > > plot(t(1:endplot),y1(1:endplot),t(1:endplot),y2(1:endplot)); > > subplot(212); > > plot(t(1:endplot),y1(1:endplot)+y2(1:endplot)); > > > > y=fft(s); > > ymax = max(abs(y)); > > y = y ./ ymax; *// Normalize* > > > > *// s is real so the fft response is conjugate symmetric* > > *// and we retain only the first N/2 points* > > f=sample_rate*(0:(N/2))/N; *//associated frequency vector* > > n=size(f,'*'); > > fftplots = scf(); > > plot(f(2:$),abs(y(2:n))); *// drop first datapoint, f = 0 (it prevents > log-plot)* > > a = gca(); > > a.log_flags = "lnn"; > > > > Best regards, > > Claus > > ___ > users mailing list > users@lists.scilab.org > http://lists.scilab.org/mailman/listinfo/users > > > ___ > users mailing list > users@lists.scilab.org > http://lists.scilab.org/mailman/listinfo/users > ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Hi, In theory they are "completely independent", but currently as a matter of fact there is a clash wrt. to the semantics of the "!" character. Does is it really make sense allowing "!" in identifier names, while keeping the the current history recall feature, and assuming, that the user prepends a space in front of expressions like "!A=1" to get them executed in the Java console? My conclusion: if both features are going to be kept, then the clash wrt "!" should be resolved ASAP, anyhow. Cheers, Wozai -- Sent from: http://mailinglists.scilab.org/Scilab-users-Mailing-Lists-Archives-f2602246.html ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Le 27/05/2018 à 10:52, Jens Simon Strom a écrit : Hi, The `!` usage to recall a previous command is discussed here in detail. I don't miss it. My question was different. I was answering to the "What's your opinion?" question by Clément. Yes, i definitely agree on that both questions are completely independent, and that since the fix for variables names is deemed /easy/, it should be applied ASAP and fastly made available in the continuous built. Regards Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Exclamation mark in variable names
Hi, The `!` usage to recall a previous command is discussed here in detail. I don't miss it. My question was different. How about implementing again the "!" as a valid character in variable names as documented? How long is the reasonable response time for fixing the reported bug? Regards Jens -- Am 26.05.2018 14:10, schrieb Samuel Gougeon: Le 25/05/2018 à 11:02, Samuel Gougeon a écrit : Hello, Le 25/05/2018 à 10:45, Clément David a écrit : Hi, Thanks for your experimental work on that topic. I guess we could merge the parser fix easily however the `!` usage to recall a previous command will remain problematic. This usage does not seem to be documented somewhere in the help page, maybe we could discard it. What's your opinion on that ? It is an historical and standard feature, used not only in Scilab language. Please see the entry http://bugzilla.scilab.org/10776 The only issue is that it is still undocumented. It could be described in the Console's page. "The only issue" : hmm, not really. Even if the missing documentation is the main one, IMO this (already) very handy feature could be improved in at least two ways: * when no match is found in the history, nothing happens. For people who does not know the feature (or who has forgotten that it is available), this could be easily puzzling and felt as a bug. => when no match is found, Scilab shall print a message "No match found in history" * A listbox listing matches could be displayed, to select the only entry searched for. This might be done in two ways : o either typing "!" + one char as the very first characters would enter a completion mode based on the history, with matches listed in a listbox as described hereabove o or this could be done only after validating with , or CTRL+space as for the feature completion (but here targeted to the history with the leading "!") If a completion mode is implemented, then the message "no match found in history" could be displayed in the listbox instead of in the console (note that the general feature completion triggered with CTRL+space displays nothing when no match is found). By the way, as for this "!" history recall, the existing interactive usage of the completion is not documented in the Console page. Let's add both in the page, as they presently are. Regards Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
