Complex Networks XI by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030409432
Publisher: Springer International Publishing

Fig. 1.Collective efficacy map of Columbus, Ohio

In the equation above, indicates the number of reports for neighborhood . indicates number of items responded in report j. We normalize the scores in range of 0 to 1 and use it as the ground truth for our study. This methodology is aligned with the traditional measurement approach employed to compute collective efficacy at neighborhood level [21–23]. Note that while we adopt a similar ground truth model [23], we lever survey reports from individuals who both reside within and frequently visit a particular neighborhood. Concomitantly, the social media postings included in our study includes postings from both individuals that reside within and frequently visit a particular neighborhood. In order to increase the reliability of the aggregation we only include the neighborhoods having at least 5 reports. Figure 1 shows a collective efficacy map of Columbus.

Twitter Data: To capture the informal language of local citizenry focused on local venues and localities, more than 50 million publicly available tweets were collected from the accounts of 54k Twitter users who identified their location as Columbus. These users were identified through Snowball sampling [24]. We excluded the tweets that did not contain a mention of locations within our study area. For doing so, we used a publicly available location name extractor LNEx [25]. LNEx extracts location entries from tweets, handles abbreviations, tackles appellation formation and metonomy pose disambiguation problems given a gazetteer and the region information. Open Street Map gazetteer was used and region was set to Columbus. In some cases locations extracted by LNEx are ambiguous. In our study, we exclude tweets containing ambiguous location entities. This pruning step resulted in 4846 unique locations that were spotted in 545k tweets and were mapped to 424 neighborhoods. For more details on our data collection and pruning steps see Appendix A.1 of the supplementary material.2

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