# Possible Bug within GraphData?

**URL:** <https://community.wolfram.com/t/possible-bug-within-graphdata/7427>\
**Category:** Ideas\
**Tags:** graphs-and-networks\
**Created:** [December 9, 2015, 3:42pm UTC](https://community.wolfram.com/t/possible-bug-within-graphdata/7427 "2015-12-09T15:42:44Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![apereiraua](https://avatars.discourse-cdn.com/v4/letter/a/3e96dc/32.png) [@apereiraua](https://community.wolfram.com/u/apereiraua)\
**Post date:** [December 9, 2015, 3:42pm UTC](https://community.wolfram.com/t/possible-bug-within-graphdata/7427/1 "2015-12-09T15:42:44Z")

</div>

I’m trying to get graphs with **no** perfect matching of order 26 using GraphData. It seems that GraphData[“NoPerfectMatching”, 26] returns several graphs that have a Perfect Matching ( NoncayleyTransite graphs). I’m using Mathematica 10.3. I’ve filled a bug to Wolfram support, but I’d appreciate if someone can confirm the following output.

Thanks in advance  
A. Pereira

```
In[1]:= l = GraphData["NoPerfectMatching", 26];

In[2]:= GraphData[#, "PerfectMatching"] & /@ l

Out[2]= {False, False, False, False, True, True, True, True, True, \
True, True, True, True, True, True, True, True, True, True, True, \
True, True, True, True, True, True, True, True, True, True, True, \
True, True, True, True, True, True, True, True, True, True, True, \
True, True, True, True, True, True, True, True, True, True, True, \
True, True, True, True, True, True, True, True, True, True, True, \
True, True, True, True, True, True, True, True, True, False, False}

```

---

<div class="post-metadata">

**Author:** ![seanc](https://yyz1.discourse-cdn.com/wolfram/user_avatar/community.wolfram.com/seanc/32/34005_2.png) [@seanc](https://community.wolfram.com/u/seanc)\
**Post date:** [December 9, 2015, 10:02pm UTC](https://community.wolfram.com/t/possible-bug-within-graphdata/7427/2 "2015-12-09T22:02:41Z")

</div>

Yes. I get the same output. The developers were able to reproduce the issue and are looking into how to resolve it.  
Thank you for taking the time to let us know about this issue.

---

<div class="post-metadata">

**Author:** ![apereiraua](https://avatars.discourse-cdn.com/v4/letter/a/3e96dc/32.png) [@apereiraua](https://community.wolfram.com/u/apereiraua)\
**Post date:** [December 9, 2015, 10:08pm UTC](https://community.wolfram.com/t/possible-bug-within-graphdata/7427/3 "2015-12-09T22:08:53Z")

</div>

Thank you for the reply. Now I know this is not a problem of my install.

---

<div class="post-metadata">

**Author:** ![cadrin](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@cadrin](https://community.wolfram.com/u/cadrin)\
**Post date:** [December 10, 2015, 11:10am UTC](https://community.wolfram.com/t/possible-bug-within-graphdata/7427/4 "2015-12-10T11:10:36Z")

</div>

GraphData[“NoPerfectMatching”, 26];

In this way, there is a result(profit).

---

<div class="post-metadata">

**Author:** ![apereiraua](https://avatars.discourse-cdn.com/v4/letter/a/3e96dc/32.png) [@apereiraua](https://community.wolfram.com/u/apereiraua)\
**Post date:** [December 15, 2015, 4:57pm UTC](https://community.wolfram.com/t/possible-bug-within-graphdata/7427/5 "2015-12-15T16:57:02Z")

</div>

Seems like Wolfram has updated the GraphData database and today it list correctly only graphs with a perfect matching:

```
In[1]:= GraphData["NoPerfectMatching", 26]

Out[1]= {{"CayleyTree", {5, 2}}, "DeltoidalIcositetrahedralGraph", {"DutchWindmill", {5, 
   6}}, {"Empty", 26}, "Octane", {"Windmill", {5, 6}}}

```

So my problem is solved for now. Lesson learned: Never trust 100% on data that is not yours. And even if it is your data, check and recheck, for consistency!