Agh, can we deprecate those wiki docs? I hate having multiple copies of the exact same thing, especially since this sort of work will lead to documentation skew.
On Fri, Jan 25, 2013 at 7:52 AM, Chris Marshall <[email protected]>wrote: > If you are talking about the wiki page, > > > http://sourceforge.net/apps/mediawiki/pdl/index.php?title=PDL_for_Matlab_users > > send me your sf.net user id and I can add you > as an editor. > > --Chris > > On Fri, Jan 25, 2013 at 2:44 AM, Lee <[email protected]> wrote: > > Thanks. I just tried logging in to SourceForge to put this (and which) on > > the Perl for Matlab page, but although I am logged in to SF, there is no > > edit link on the project page. Is this something for which I need to > apply? > > > > > > On 24/01/2013 17:43, David Mertens wrote: > >> > >> I only briefly touched on "where". The "where" function is pretty > awesome > >> compared with Matlab because you can actually save the "slice" in a > variable > >> and manipulate it later. In Matlab, as I recall, you can only > manipulate a > >> slice on the line in which the slice is created. In PDL, you can store > the > >> slice in a variable and manipulate it later. > >> > >> $a = sequence(20); > >> $b = $a->where($a % 2 == 0); > >> # Make all even values in $a odd: > >> $b += 1; > >> > >> > >> On Thu, Jan 24, 2013 at 10:40 AM, David Mertens < > [email protected] > >> <mailto:[email protected]>> wrote: > >> > >> Just to clarify, here's something out of the pdl shell: > >> > >> # make 20 values from -9 to 10 > >> pdl> $a = zeroes(20)->xlinvals(-9, 10) > >> pdl> p $a > >> [-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10] > >> > >> # get a mask of true/false > >> pdl> p $a == 4 > >> [0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0] > >> > >> # Get that offset: > >> pdl> p which($a == 4) > >> [13] > >> > >> # Mask all values that are even: > >> pdl> p $a % 2 == 0 > >> [0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1] > >> > >> # Get those indices > >> pdl> p which($a % 2 == 0) > >> [1 3 5 7 9 11 13 15 17 19] > >> > >> # Flip the sign of even values > >> pdl> $a->where($a % 2 == 0) *= -1 > >> pdl> p $a > >> [-9 8 -7 6 -5 4 -3 2 -1 0 1 -2 3 -4 5 -6 7 -8 9 -10] > >> > >> # learn about approx: > >> pdl> ? approx > >> # use it for floating point numbers > >> pdl> $a = sequence(20)->sqrt > >> pdl> p $a > >> [0 1 1.4142136 1.7320508 2 2.236068 2.4494897 2.6457513 > >> 2.8284271 3 3.1622777 3.3166248 3.4641016 3.6055513 3.7416574 > >> 3.8729833 4 4.1231056 4.2426407 4.3588989] > >> > >> # Find the square root of 2, approximately: > >> pdl> p $a->approx(1.414) > >> [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] > >> > >> # The default epsilon, 1e-6, is too strict. > >> # Find where $a is approximately 1.414, within 1e-3 > >> pdl> p $a->approx(1.414, 1e-3) > >> [0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] > >> > >> # Later calls to approx use same "epsilon" that we just set: > >> pdl> p $a->approx(1.414) > >> [0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0] > >> > >> # Get the index thereof > >> pdl> p which($a->approx(1.414)) > >> [2] > >> > >> Hope that helps! > >> > >> > >> On Thu, Jan 24, 2013 at 10:23 AM, Lee Goddard <[email protected] > >> <mailto:[email protected]>> wrote: > >> > >> Thanks. > >> > >> > >> On 24/01/2013 15:50, Chris Marshall wrote: > >> > >> which or whichND > >> > >> On Thu, Jan 24, 2013 at 9:46 AM, Lee Goddard > >> <[email protected] <mailto:[email protected]>> wrote: > >> > >> Is there a PDL equivalant to MATLAB's 'find(x)' > >> function, or will I need to > >> write my own? > >> > >> TIA > >> Lee > >> > >> ind = find(X) > >> locates all nonzero elements of array X, and returns > >> the linear indicies of > >> those elements in vector ind. If X is a row vector, > >> then ind is a row > >> vector; otherwise, ind is a column vector. If X > >> contains no nonzero elements > >> or is an empty array, then ind is an empty array. > >> > >> -- http://www.mathworks.com/help/matlab/ref/find.html > >> > >> > >> _______________________________________________ > >> Perldl mailing list > >> [email protected] <mailto:[email protected]> > >> > >> http://mailman.jach.hawaii.edu/mailman/listinfo/perldl > >> > >> > >> > >> _______________________________________________ > >> Perldl mailing list > >> [email protected] <mailto:[email protected]> > >> > >> http://mailman.jach.hawaii.edu/mailman/listinfo/perldl > >> > >> > >> > >> > >> -- "Debugging is twice as hard as writing the code in the first > >> place. > >> Therefore, if you write the code as cleverly as possible, you are, > >> by definition, not smart enough to debug it." -- Brian Kernighan > >> > >> > >> > >> > >> -- > >> "Debugging is twice as hard as writing the code in the first place. > >> Therefore, if you write the code as cleverly as possible, you are, > >> by definition, not smart enough to debug it." -- Brian Kernighan > >> > >> > >> _______________________________________________ > >> Perldl mailing list > >> [email protected] > >> http://mailman.jach.hawaii.edu/mailman/listinfo/perldl > > > > > > > > _______________________________________________ > > Perldl mailing list > > [email protected] > > http://mailman.jach.hawaii.edu/mailman/listinfo/perldl > > _______________________________________________ > Perldl mailing list > [email protected] > http://mailman.jach.hawaii.edu/mailman/listinfo/perldl > -- "Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." -- Brian Kernighan
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