Metapost labeling question. Please help

Metapost labeling question. Please help

[Curiouslearn]

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Hi,
I want the labels as (0.5,0.55,0.6,0.65,0.7,...,1)
or (0.50,0.55,0.60,0.65,0.70,...,1). Either of these two is fine.

I tried the following code for this.

\starttext

\startuseMPgraphic{labeltest}
numeric rmin,rmax;
rmin := 0.5; rmax := 1;
ux := 25cm; uy :=10cm;
% draw axes
draw (rmin,0)*ux -- (rmax+0.1,0)*ux;
draw (rmin,0)*ux -- (rmin*ux,(1.1)*uy);
for x = 0.5 step 0.05 until 1.1:
label.bot(textext(decimal(x)),(x*ux,x*uy));
endfor;
\stopuseMPgraphic

\useMPgraphic{labeltest}

\stoptext

I get (0.5,0.55, 0.6,0.65001,0.70001,0.75002,...,1.00003) instead. I don't
understand why I get more than 2 digits after 0.6. Is there a way to
restrict the number of digits after the decimal point.

Thanks very much.

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Re: Metapost labeling question. Please help

[Mojca Miklavec]

On Fri, Apr 3, 2009 at 03:02, Curiouslearn wrote:
> Hi,
> I want the labels as (0.5,0.55,0.6,0.65,0.7,...,1)
> or (0.50,0.55,0.60,0.65,0.70,...,1). Either of these two is fine.
> I tried the following code for this.
> \starttext
> \startuseMPgraphic{labeltest}
> numeric rmin,rmax;
> rmin := 0.5; rmax := 1;
> ux := 25cm; uy :=10cm;
> % draw axes
> draw (rmin,0)*ux -- (rmax+0.1,0)*ux;
> draw (rmin,0)*ux -- (rmin*ux,(1.1)*uy);
> for x = 0.5 step 0.05 until 1.1:
> label.bot(textext(decimal(x)),(x*ux,x*uy));
> endfor;
> \stopuseMPgraphic
> \useMPgraphic{labeltest}
> \stoptext
> I get (0.5,0.55, 0.6,0.65001,0.70001,0.75002,...,1.00003) instead. I don't
> understand why I get more than 2 digits after 0.6.

It's because you get exact numbers in the terms what metapost
considers exact (multiples of 2^{-something}). You have exactly the
same problem if you work with floating points with any other
programming language.

> Is there a way to
> restrict the number of digits after the decimal point.
> Thanks very much.

See page 18 of metapost manual (speaking of metapost manual present in
TeX Live):

-----
6.2 Operators

The length operator returns the number of characters in a string.
For substring construction, the ⟨of operator⟩ substring is used like this:
    substring ⟨pair expression⟩ of ⟨string primary⟩
substring (2,4) of "abcde" is "cd".
-----

You can use substring (0,4) to truncate the number. 0.5 might need
special treatment, so you either need to concatenate it with 0 at the
end or you need to check the lenght of string before using substring.

Mojca
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Re: Metapost labeling question. Please help

[Peter Rolf]

Curiouslearn schrieb:
> Hi,
>
> I want the labels as (0.5,0.55,0.6,0.65,0.7,...,1) 
> or (0.50,0.55,0.60,0.65,0.70,...,1). Either of these two is fine.
>
> I tried the following code for this.
>
> \starttext
>
> \startuseMPgraphic{labeltest}
> numeric rmin,rmax;
> rmin := 0.5; rmax := 1;
> ux := 25cm; uy :=10cm;
> % draw axes
> draw (rmin,0)*ux -- (rmax+0.1,0)*ux;
> draw (rmin,0)*ux -- (rmin*ux,(1.1)*uy);
> for x = 0.5 step 0.05 until 1.1:
> label.bot(textext(decimal(x)),(x*ux,x*uy));
you accumulate the rounding error with every step of the loop. try to 
avoid such 'low value' steps if possible.

for x = 10 step 1 until 22: % 0.05*20 to get an integer loop index
tx := x/20; % correct value
label.bot(textext(decimal(tx)),(tx*ux,tx*uy));


Best wishes,  Peter

> endfor;
> \stopuseMPgraphic
>
> \useMPgraphic{labeltest}
>
> \stoptext
>
> I get (0.5,0.55, 0.6,0.65001,0.70001,0.75002,...,1.00003) instead. I 
> don't understand why I get more than 2 digits after 0.6. Is there a 
> way to restrict the number of digits after the decimal point. 
>
> Thanks very much. 
>
>
> ------------------------------------------------------------------------
>
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
>
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
> archive  : https://foundry.supelec.fr/projects/contextrev/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________
>   


-- 
  "Es ist doch ein Trost,
   das Geldgier manchmal blöd macht."

             - Kottan in "Kottan ermittelt", Folge 9: "Die Einteilung" -



___________________________________________________________________________________
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maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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archive  : https://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________

Re: Metapost labeling question. Please help

[Curiouslearn]

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Mojca and Peter, thanks very much for your responses. I used Peter's
solution and it worked beautifully.
Does anyone know how I can change the size of these labels? If I try

textext(\tfa decimal(tx))

that does not work.

On Fri, Apr 3, 2009 at 6:52 AM, Peter Rolf <indiego@gmx.net> wrote:

> Curiouslearn schrieb:
>
>> Hi,
>>
>> I want the labels as (0.5,0.55,0.6,0.65,0.7,...,1) or
>> (0.50,0.55,0.60,0.65,0.70,...,1). Either of these two is fine.
>>
>> I tried the following code for this.
>>
>> \starttext
>>
>> \startuseMPgraphic{labeltest}
>> numeric rmin,rmax;
>> rmin := 0.5; rmax := 1;
>> ux := 25cm; uy :=10cm;
>> % draw axes
>> draw (rmin,0)*ux -- (rmax+0.1,0)*ux;
>> draw (rmin,0)*ux -- (rmin*ux,(1.1)*uy);
>> for x = 0.5 step 0.05 until 1.1:
>> label.bot(textext(decimal(x)),(x*ux,x*uy));
>>
> you accumulate the rounding error with every step of the loop. try to avoid
> such 'low value' steps if possible.
>
> for x = 10 step 1 until 22: % 0.05*20 to get an integer loop index
> tx := x/20; % correct value
> label.bot(textext(decimal(tx)),(tx*ux,tx*uy));
>
>
> Best wishes,  Peter
>
>  endfor;
>> \stopuseMPgraphic
>>
>> \useMPgraphic{labeltest}
>>
>> \stoptext
>>
>> I get (0.5,0.55, 0.6,0.65001,0.70001,0.75002,...,1.00003) instead. I don't
>> understand why I get more than 2 digits after 0.6. Is there a way to
>> restrict the number of digits after the decimal point.
>> Thanks very much.
>>
>> ------------------------------------------------------------------------
>>
>>
>> ___________________________________________________________________________________
>> If your question is of interest to others as well, please add an entry to
>> the Wiki!
>>
>> maillist : ntg-context@ntg.nl /
>> http://www.ntg.nl/mailman/listinfo/ntg-context
>> webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
>> archive  : https://foundry.supelec.fr/projects/contextrev/
>> wiki     : http://contextgarden.net
>>
>> ___________________________________________________________________________________
>>
>>
>
>
> --
>  "Es ist doch ein Trost,
>  das Geldgier manchmal blöd macht."
>
>            - Kottan in "Kottan ermittelt", Folge 9: "Die Einteilung" -
>
>
>
>
>
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to
> the Wiki!
>
> maillist : ntg-context@ntg.nl /
> http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
> archive  : https://foundry.supelec.fr/projects/contextrev/
> wiki     : http://contextgarden.net
>
> ___________________________________________________________________________________
>

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___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : https://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________

Re: Metapost labeling question. Please help

[Wolfgang Schuster]

Am 03.04.2009 um 14:47 schrieb Curiouslearn:

> Mojca and Peter, thanks very much for your responses. I used Peter's  
> solution and it worked beautifully.
>
> Does anyone know how I can change the size of these labels? If I try
>
> textext(\tfa decimal(tx))

textext("\tfa" & decimal(tx))

Wolfgang

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wiki     : http://contextgarden.net
___________________________________________________________________________________

Re: Metapost labeling question. Please help

[Curiouslearn]

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Beautiful! Thanks, Wolfgang.

On Fri, Apr 3, 2009 at 9:35 AM, Wolfgang Schuster <
schuster.wolfgang@googlemail.com> wrote:

>
> Am 03.04.2009 um 14:47 schrieb Curiouslearn:
>
>  Mojca and Peter, thanks very much for your responses. I used Peter's
>> solution and it worked beautifully.
>>
>> Does anyone know how I can change the size of these labels? If I try
>>
>> textext(\tfa decimal(tx))
>>
>
> textext("\tfa" & decimal(tx))
>
> Wolfgang
>
>
>
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to
> the Wiki!
>
> maillist : ntg-context@ntg.nl /
> http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
> archive  : https://foundry.supelec.fr/projects/contextrev/
> wiki     : http://contextgarden.net
>
> ___________________________________________________________________________________
>

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___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : https://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________