# Add a grid to your graphs

**URL:** <https://forum.graphviz.org/t/add-a-grid-to-your-graphs/2402>\
**Category:** Show and Tell\
**Created:** [August 18, 2024, 8:39pm UTC](https://forum.graphviz.org/t/add-a-grid-to-your-graphs/2402 "2024-08-18T20:39:05Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![somms](https://sea2.discourse-cdn.com/graphviz/user_avatar/forum.graphviz.org/somms/32/1839_2.png) [@somms](https://forum.graphviz.org/u/somms)\
**Post date:** [February 14, 2025, 6:03pm UTC](https://forum.graphviz.org/t/add-a-grid-to-your-graphs/2402/6 "2025-02-14T18:03:25Z")

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Moving the conversation to this thread from [Simulate Y axis and horizontal strips - #5 by somms](https://forum.graphviz.org/t/simulate-y-axis-and-horizontal-strips/2723/5)

I get an error that may be related to your code (or most probably to my inexperience)

When I try to add any parameter using the -a option, I always get an empty output and a “gvpr: gvpr” message:

```auto
$ dot input.dot | gvpr -a 'size=rank' -cf addGrid.gvpr
// SIZE start: 72pt delta: 0
// SIZE end: 72pt size: 72 delta: 0
// ARG >size=rank<
// type: s
gvpr: gvpr

```

The “offending line” is

187 Val=substr(ARGV[i],Indx);

After adding some prints to debug, the problem is that Indx value is -3.

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