R语言按照城市取样(一个城市有多行观测,想筛选一些城市) select():仅能筛选变量 数据整理—dplyr包(filter系列) subset():既可以筛选观测也可以筛选变量 R语言数据的查询筛选-subset()
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The ability to achieve the high flow and influent solids concentrations in the existing tanks saved site space and construction costs.doi:10.2175/193864706783751104Baumann, P.Kieffer, C.Morrall, T.Bauer, R.Proceedings of the Water Environment Federation...
Bin Laden Killed: Who Breaks the Story? A Random Tweeter On A Break – Not FOX News, CNN Or ABCRonn Torossian