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if function to assign zeros to y-values

 
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Roberto



Joined: 16 Mar 2008
Posts: 102
Location: Netherlands Beek en Donk

PostPosted: Sat Jan 24, 2015 2:58 pm    Post subject: if function to assign zeros to y-values Reply with quote

Hi,

Somehow I cannot manage to realize replacing y-values by zeros using the operate on Y function.

In a graph I want Y-values of the X-range larger than 128 to be zero.

Using the "operate on Y command I tried several varieties of the if-function like below but everything ends up in a "syntax error":

Y= if(X>128,0,Y*1)
Y= if(X>128,(0*Y),(Y*1))
Y= if(Y<0,0*Y,Y) (Y values happen to be negative when X>128; abused this coïncidence in the latter example)
etc.

I don't see what I'm doing anything different than the example in the help: if(x<5,x^2,(10-x)^2)

Can anyone help me with this one?
The orginal graph is a sine curve with X[0,255] and Y[-127,127]

Roberto
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DPlotAdmin
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Joined: 24 Jun 2003
Posts: 2310
Location: Vicksburg, Mississippi

PostPosted: Sat Jan 24, 2015 6:58 pm    Post subject: Reply with quote

Quote:
Y= if(X>128,0,Y*1)


I tried this just now and it worked as expected. Also "if(X>128,0,Y)" works. What version are you using?




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Roberto



Joined: 16 Mar 2008
Posts: 102
Location: Netherlands Beek en Donk

PostPosted: Sat Jan 24, 2015 7:38 pm    Post subject: Reply with quote

Really??!

Tried again and still syntax error. I'm using Dplot 2.3.5.3 which is the latest as far as I am aware of.

Adding the "=" before the if function doesn't help either (in the help example the "=" isn't used).
Also setting the "radians" option in the dialog does not do the trick.

Following an image of all info regarding this issue. Can you discover what I'm doing wrong, David?



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DPlotAdmin
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Joined: 24 Jun 2003
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Location: Vicksburg, Mississippi

PostPosted: Sun Jan 25, 2015 1:37 am    Post subject: Reply with quote

I'm at a loss presently, sorry. The leading equals sign is redundant and is removed before the equation is ever evaluated. It looked like you might have a space between ">" and "128" (and it would have been embarrassing if that was the problem), but I tried one and then several spaces and it worked as expected.

The only thing I can think of at the moment is there's a problem with internationalization and interpreting a comma as a decimal point. But I'll be surprised if that's it. What country do you reside in?
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Roberto



Joined: 16 Mar 2008
Posts: 102
Location: Netherlands Beek en Donk

PostPosted: Sun Jan 25, 2015 5:16 am    Post subject: Reply with quote

Netherlands is my location.
(PS: guess you overlooked the location being mentioned on the left of the posted messages Smile )

Number 10,95
Large Number 10.000,95
(opposite of English: dots between integers, comma before fraction)

If I use dots instead of commas in the if expression still an error message.

------------------

I un- and reïnstalled DPlot using the backup copy I had.

Experimenting a bit with other (operate on) Y=f(X) expressions and the Decimal Point set option in Options I got interesting results. Looks indeeds like your hunch was in the right direction:



Notice the dots in the expression history! "Without" any reason they changed to comma's !

-------------

I cannot download a replacement installer for DPlot telling me there are no updates.
If you think it might help, could you please send me the latest release to roberto@romus.nl ? Long shot but my copy of DPlot might be corrupted eventhough a corrupted file likely would cause much more severe issues.
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PostPosted: Sun Jan 25, 2015 1:57 pm    Post subject: Reply with quote

You have the latest version already. I'll play around with commas and decimal points and figure this out. I think what likely happened is that older versions did NOT (regardless of your internationalization settings) see a comma as a decimal separator, but the current version will.
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