* Example generated by -dataex-. To install: ssc install dataex
clear
input str45 city float(ratio_10zt ratio_10zc)
"北京市"   .02025706 .1088817
"北京市"  .033003196 .1088817
"北京市"  .025289273 .1088817
"北京市"    .0497345 .1088817
"北京市"   .05917925 .1088817
"北京市"  .014679958 .1088817
"北京市"  .012532453 .1088817
"北京市"   .04912551 .1088817
"北京市"  .023547763 .1088817
"北京市"   .01940233 .1088817
"北京市"   .03190273 .1088817
"北京市"   .01637873 .1088817
"北京市"  .016432151 .1088817
"北京市"    .0196908 .1088817
"北京市"   .01637873 .1088817
"北京市"   .03215915 .1088817
"北京市"  .034125026 .1088817
"北京市"  .019541224 .1088817
"北京市"    .0256739 .1088817
"北京市"   .04487323 .1088817
"北京市"   .02830219 .1088817
"北京市" .0004273641 .1088817
"北京市"  .004626217 .1088817
"北京市"  .001036358 .1088817
"北京市" .0004273641 .1088817
"北京市"   .06540808 .1088817
"北京市"  .013964123 .1088817
"北京市"  .019925853 .1088817
"北京市"  .010812312 .1088817
"北京市"   .04647585 .1088817
"北京市"   .02080195 .1088817
"北京市"   .01897497 .1088817
"北京市"  .018237764 .1088817
"北京市"   .07113476 .1088817
"北京市"   .04526855 .1088817
"北京市"   .07075013 .1088817
"北京市"   .01632531 .1088817
"北京市"   .01897497 .1088817
"深圳市"  .013964123 .0547774
"深圳市"   .04487323 .0547774
"深圳市"   .01632531 .0547774
"深圳市"   .03190273 .0547774
"深圳市"   .05917925 .0547774
"深圳市"   .02025706 .0547774
"深圳市"  .016432151 .0547774
"深圳市"    .0196908 .0547774
"深圳市"  .023547763 .0547774
"深圳市"  .014679958 .0547774
"深圳市"  .019925853 .0547774
"深圳市"  .012532453 .0547774
"深圳市"   .07075013 .0547774
"深圳市"  .033003196 .0547774
"深圳市"   .07113476 .0547774
"深圳市"   .04912551 .0547774
"深圳市"   .01940233 .0547774
"深圳市"   .04647585 .0547774
"深圳市"  .025289273 .0547774
"深圳市"  .019541224 .0547774
"深圳市"  .016432151 .0547774
"深圳市"   .02080195 .0547774
end

有若干观测值和变量，要求依据ratio_10zc（第三列）从高到低给city排名。
即ratio_10zc=.1088817，"北京市"的全部观测值排名第一。使用rank(-ratio_10zc)出来不对。