gnuplot-info

[Gnuplot-info] wrong prompt while using 'update' command after 'fit'

[boluor <bo...@si...>]

i first define a function : f(x) = a *x**2 + b *x + c;

then : fit f(x) 'data' via a,b,c;

then i want to store the a,b,c to a file names 'a.log'.

so i typed : update 'a.log'

but i got the wrong prompt : 

  gnuplot> update 'a.log'
         Could not rename file a.log to a.log.old

i want to know why??

i use gnuplot Version 4.2 patchlevel 5 , under ubuntu linux9.10.

thank u all. 

Re: [Gnuplot-info] wrong prompt while using 'update' command after 'fit'

[Hans-Bernhard B. <HBB...@t-...>]

boluor wrote:
> then : fit f(x) 'data' via a,b,c;
> 
> then i want to store the a,b,c to a file names 'a.log'.
> 
> so i typed : update 'a.log'

That "so" expresses an incorrect conclusion.  The 'update' command is 
not for creating a new file from scratch.  It's for _updating_ an 
already existing file, thus the name.

There usually isn't much point in using the 'update' command if your fit 
command's "via" argument wasn't a file.

> but i got the wrong prompt : 
> 
>   gnuplot> update 'a.log'
>          Could not rename file a.log to a.log.old

That's not a prompt, it's an error message.  It tells you (somewhat 
indirectly) that you didn't have a file 'a.log' to be updated.