Hi all,

I am trying to code used to replace values of one variable with other values from different variable.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(pre1 pre2 pre3 pre4 pre5 pre6 pre7 pre8 pre9 pre10 pre11 pre12 pre13 pre14 pre15 pre16 pre17 pre18 pre19 pre20 pre21 crv5_ crv7_ crv8_ crv9_ crv10_ crv11_ crv12_ crv13_ crv14_ crv15_ crv16_ crv17_ crv18_ crv19_)
. . . . . . . . . . . . . . . . . . . . .  1.420813e-10  1.538471e-06   .0030466826     .00641038   .009309801    .026179815     .08466652     .08571296     .17514174     .24400574     .15538634     .17509454     .03229719    .002746747
. . . . . . . . . . . . . . . . . . . . .  .00006437384    .014297502     .38144755      .1563745     .1026714     .12815352     .12850326     .04299963    .031593457    .011509055   .0018745286   .0005022692  8.872414e-06  7.404656e-08
. . . . . . . . . . . . . . . . . . . . .  4.663782e-18 1.9553883e-12 2.6198393e-07 1.6389433e-06 4.763092e-06 .000029164466   .0002974402   .0007629592     .00424578    .021396916     .04420042     .25058898     .37056875      .3079029
. . . . . . . . . . . . . . . . . . . . . 1.0865772e-20 1.3506045e-14  6.395264e-09   5.36199e-08 1.901735e-07  1.473112e-06 .000021332846  .00007103983    .000537118   .0039952984    .011536729     .11203518     .30441836      .5673832
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . . 1.5554887e-13  8.119904e-09  .00009769932   .0003373321   .000663544   .0026016266    .013705858     .02092475    .065428406      .1577846     .16845314      .3664564      .1671602     .03638645
. . . . . . . . . . . . . . . . . . . . .  4.432053e-06    .002538139     .18728225      .1246691    .10005043     .15218854      .2023386     .08995057     .08459818     .04274843     .00983818    .003674394  .00011702513  1.737149e-06
. . . . . . . . . . . . . . . . . . . . .  1.930359e-08  .00005772203    .026592746    .035485834     .0399411     .08576635      .1873456     .13358808      .1938521     .17308015     .07124478     .04866727    .004210783  .00016747718
. . . . . . . . . . . . . . . . . . . . .  .00013831006    .022900587      .4484086       .155492    .09581362     .11245997     .10333547    .031590864     .02150091    .007073301   .0010327316   .0002499707  3.667307e-06 2.5542525e-08
. . . . . . . . . . . . . . . . . . . . .  3.416533e-12   8.96909e-08  .00048944965    .001369852    .00236238    .008006947    .034042504     .04352798     .11290028      .2140593       .182728      .2962125     .09118113      .0131196
. . . . . . . . . . . . . . . . . . . . . 2.7831446e-12   7.65663e-08   .0004409111    .001252145  .0021789365    .007458689     .03217628      .0416462     .10939837     .21083854     .18276106      .3021616     .09554887     .01413835
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . .     .02444949     .34704915      .5731633     .03207296   .011287073    .007854286    .003458914   .0004719603  .00016830266 .000023152586 1.2896116e-06 1.3433531e-07  3.891738e-10   5.62472e-13
. . . . . . . . . . . . . . . . . . . . .  .00007738412    .016031174      .3973496     .15668233    .10134303       .124666      .1224445     .04010816     .02893927    .010290721   .0016333666   .0004272129  7.222545e-06   5.77539e-08
. . . . . . . . . . . . . . . . . . . . .  6.225233e-06    .003180121     .20724833     .13064294    .10236664      .1520457     .19537337     .08397492     .07665811     .03724017    .008224747    .002949925  .00008756543  1.213253e-06
. . . . . . . . . . . . . . . . . . . . .  5.711757e-06    .003003969       .202052     .12915957    .10182344     .15215944       .197224      .0855025     .07864742     .03859181   .0086132325    .003121239  .00009432836 1.3301212e-06
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . .  7.479014e-13  2.766093e-08   .0002238192   .0006963295  .0012825185    .004673998    .022109233     .03089581     .08794674      .1879665      .1794586      .3364218     .12604964     .02227501
. . . . . . . . . . . . . . . . . . . . . 1.9768643e-07   .0003020521     .06566214     .06728765    .06611959     .12340982     .22013944     .12998039     .15804556     .11196984      .0365051      .0194239   .0011243086   .0000300288
. . . . . . . . . . . . . . . . . . . . . 1.7802686e-09   .0000101362    .009663225    .016311053    .02087387     .05128955     .13624771     .11598107      .1996272     .22261417     .11418645     .09981927    .012640782    .000735507
. . . . . . . . . . . . . . . . . . . . . .000015732547    .005835186     .26908162     .14480214    .10606255     .14735782     .17211884     .06725853     .05648119      .0245689    .004831323    .001548042   .0000376888 4.3016075e-07
. . . . . . . . . . . . . . . . . . . . . 1.2309873e-15 1.7600225e-10  6.778836e-06  .00003140686 .00007472478   .0003631671   .0026281385    .005173804     .02133938     .07338617     .10815435     .36927125      .2982127     .12135816
. . . . . . . . . . . . . . . . . . . . . 1.4699221e-08  .00004741121     .02378473    .032655656    .03731798     .08141199     .18195927       .132503      .1961638      .1797775     .07595441     .05339102     .00483218   .0002009945
. . . . . . . . . . . . . . . . . . . . .  .00009772538    .018516937      .4177502     .15660757    .09936238     .11996747      .1147443     .03656965     .02577977    .008887726     .00136464    .000346068  5.530052e-06  4.185778e-08
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . .  2.200096e-08  .00006342677    .028044706    .036909204    .04123942      .0878805      .1898518     .13400628      .1925908     .16980077     .06902045     .04650248   .0039369157   .0001532351
. . . . . . . . . . . . . . . . . . . . .   8.74527e-11 1.0668475e-06    .002420652    .005298589   .007876478      .0227117      .0761929      .0796256     .16798724      .2439256      .1616388     .19109465     .03777904    .003447664
. . . . . . . . . . . . . . . . . . . . .   9.86672e-15    9.2322e-10 .000021780725  .00008932268  .0001962402   .0008711708    .005513462     .00976045      .0358137     .10604044     .13655724      .3845895     .24438936     .07615732
. . . . . . . . . . . . . . . . . . . . .   .0004772772     .04777861      .5547145     .14125688    .07795527       .082321     .06512605     .01700824     .01015191   .0028022644   .0003383679  .00006887862   7.32511e-07  3.731328e-09
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . .  1.382776e-09 8.4100875e-06    .008640654    .014927684    .01935464     .04821897      .1306954     .11326978      .1984135     .22636737     .11873664      .1064987    .014020106   .0008481631
. . . . . . . . . . . . . . . . . . . . .  7.371245e-15  7.325238e-10  .00001852672  .00007731687  .0001718025   .0007725425    .004983033    .008956077     .03341133     .10104962     .13265586      .3838606     .25238574     .08165754
. . . . . . . . . . . . . . . . . . . . .  3.533416e-11  5.367582e-07   .0015648413    .003680154    .00570938    .017241038     .06188371    .068546295     .15338926     .24036573     .17132632     .22141483     .04971202    .005165862
. . . . . . . . . . . . . . . . . . . . .  4.013545e-08  .00009764305    .035684004      .0440068    .04751841     .09773317      .2005741     .13502589       .185556      .1543016     .05914929     .03739148    .002860873  .00010070638
. . . . . . . . . . . . . . . . . . . . .       .146914     .57610166     .27103055    .004148152  .0010629876   .0005582546  .00016618687 .000014277997  3.603853e-06  3.083858e-07  9.980185e-09  6.657469e-10   7.81153e-13   4.71743e-16
. . . . . . . . . . . . . . . . . . . . .  6.792519e-06    .003368762     .21260795     .13212207    .10288516     .15187594     .19344084      .0824197     .07465997     .03590137   .0078447955    .002784368   .0000811558 1.1045282e-06
. . . . . . . . . . . . . . . . . . . . .  .00023336885    .031381764      .4944887        .15145    .08918554     .10020955     .08655431    .024802873     .01598968    .004892774   .0006606823   .0001488482 1.9128208e-06 1.1711734e-08
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . .   9.87591e-08   .0001852767     .05062721     .05637298    .05775486     .11251378      .2134942      .1336015      .1714527     .13036391     .04566101    .026204644    .001716061  .00005177949
. . . . . . . . . . . . . . . . . . . . . 2.4211585e-07   .0003481099    .070727564     .07068649    .06860321     .12643145      .2214434     .12850748      .1537795     .10669007     .03405015    .017718185   .0009886513  .00002546704
. . . . . . . . . . . . . . . . . . . . . 4.1207915e-07   .0005041448     .08563372     .08000084    .07512136      .1338603      .2233571     .12377687     .14197627      .0931756    .028096253    .013783229   .0006975926 .000016321488
. . . . . . . . . . . . . . . . . . . . .  .00005279573    .012630104      .3645571     .15569603     .1038698     .13167919     .13498788     .04620522    .034612022      .0129374   .0021658828   .0005954956 .000011022436  9.627696e-08
. . . . . . . . . . . . . . . . . . . . .  4.195276e-09 .000019035517    .014034597     .02184544    .02672476     .06261673     .15522756     .12419013      .2012488      .2074922     .09852562     .07889093    .008739511   .0004447356
. . . . . . . . . . . . . . . . . . . . . 1.2491035e-09  7.800611e-06    .008258502    .014400246    .01876863     .04701891     .12847514     .11214804      .1978358      .2277815     .12055216     .10924847    .014607187    .000897576
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
. . . . . . . . . . . . . . . . . . . . .  .00009748842    .018489296      .4175369      .1566111    .09938468     .12001785     .11482436     .03660569    .025811456    .008901535   .0013672354   .0003468383  5.545634e-06  4.199988e-08
. . . . . . . . . . . . . . . . . . . . .   .0008490111     .06635578      .5977817     .12933302    .06755557     .06771101     .04976092      .0120105    .006719737   .0017007086  .00018679987 .000034930843   3.16538e-07 1.3803058e-09
. . . . . . . . . . . . . . . . . . . . .   .0014281237     .08849718      .6297351      .1161102     .0575724     .05494088     .03767611     .00843862   .0044429223   .0010362626   .0001040617 .000017972205 1.4000278e-07 5.2717725e-10
. . . . . . . . . . . . . . . . . . . . .     .14222886      .5738478      .2776126   .0043824874  .0011311137   .0005977574  .00017949633 .000015583995 3.9637544e-06 3.4279574e-07 1.1230338e-08  7.565779e-10   9.05942e-13  5.579114e-16
. . . . . . . . . . . . . . . . . . . . .  8.137403e-09  .00003087388    .018598389      .0271215    .03201694    .072259806     .16965553     .12921666     .19969645     .19355987      .0864612     .06464544     .00644237   .0002949633
. . . . . . . . . . . . . . . . . . . . .     .24860124     .58354634      .1658999    .001435535  .0003231849  .00015172327  .00003866506  2.748065e-06  6.045692e-07   4.27598e-08 1.1096662e-09  6.200218e-11  5.051515e-14  2.141888e-17
. . . . . . . . . . . . . . . . . . . . .   .0003257327     .03823438     .52318805     .14736404    .08423046       .091977      .0762949    .020951144     .01303596   .0038042134   .0004879763   .0001049153 1.2359287e-06  6.953635e-09
. . . . . . . . . . . . . . . . . . . . .      .2622057     .58035177     .15573716   .0012608147 .00027966892  .00012963015  .00003245663  2.257163e-06  4.888744e-07 3.3834052e-08  8.561264e-10  4.688139e-11  3.663736e-14 1.4919074e-17
. . . . . . . . . . . . . . . . . . . . .     .07042101        .49665      .4147084     .01178584  .0034969284   .0020889633    .000743706  .00007915235  .00002339871 2.4896146e-06  1.035096e-07 8.4647676e-09 1.5058954e-11 1.3589284e-14
. . . . . . . . . . . . . . . . . . . . .    .018322403      .3087128      .6028496     .03939577   .014445047    .010432255    .004838905   .0007008064  .00026160083  .00003830219  2.289172e-06 2.5296734e-07  8.244482e-10 1.3352442e-12
. . . . . . . . . . . . . . . . . . . . .      .1256432     .56382877      .3027121    .005360195   .001420921   .0007686496   .0002384135  .00002152403  5.633588e-06 5.0686475e-07  1.738065e-08 1.2149368e-09 1.5691892e-12 1.0396132e-15
. . . . . . . . . . . . . . . . . . . . .     .03809432      .4095334     .51575696     .02223603   .007316635     .00479273   .0019399498  .00024005736   .0000794721  9.876368e-06 4.9022987e-07  4.639294e-08 1.1087609e-10 1.3306054e-13
. . . . . . . . . . . . . . . . . . . . .             .             .             .             .            .             .             .             .             .             .             .             .             .             .
end
I would like to replace "pre5" with "crv5_", "pre7" with "crv7_", and so on. So, I coded as follows:

Code:
forvalues j = 1/21{
    replace pre`j'=crv`j'_ if pre`j'==.
    }
When I ran the above code, I received the error message "crv1_ not found." I understand the why.
I could simply make commands such as "replace pre5=crv5_ if pre5==.". However, I need to run the above cods every quarter and each quarter gives "crv`j'_" with different "j".
Could you please help me to write codes that replace values only if "crv`j'_" exists?

Thanks in advance.