File:  [LON-CAPA] / loncom / homework / default_homework.lcpm
Revision 1.43: download - view: text, annotated - select for diffs
Thu Dec 13 23:38:28 2001 UTC (22 years, 4 months ago) by albertel
Branches: MAIN
CVS tags: HEAD
- seems like web should output the web argument for answer target. since the answer will be going to the web.

    1: # The LearningOnline Network with CAPA 
    2: # used by lonxml::xmlparse() as input variable $safeinit to Apache::run::run()
    3: #
    4: # $Id: default_homework.lcpm,v 1.43 2001/12/13 23:38:28 albertel Exp $
    5: #
    6: # Copyright Michigan State University Board of Trustees
    7: #
    8: # This file is part of the LearningOnline Network with CAPA (LON-CAPA).
    9: #
   10: # LON-CAPA is free software; you can redistribute it and/or modify
   11: # it under the terms of the GNU General Public License as published by
   12: # the Free Software Foundation; either version 2 of the License, or
   13: # (at your option) any later version.
   14: #
   15: # LON-CAPA is distributed in the hope that it will be useful,
   16: # but WITHOUT ANY WARRANTY; without even the implied warranty of
   17: # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   18: # GNU General Public License for more details.
   19: #
   20: # You should have received a copy of the GNU General Public License
   21: # along with LON-CAPA; if not, write to the Free Software
   22: # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   23: #
   24: # /home/httpd/html/adm/gpl.txt
   25: #
   26: # http://www.lon-capa.org/
   27: #
   28: #
   29: # Guy Albertelli
   30: #
   31: # 05/25/2001 H. K. Ng
   32: # 05/31/2001 H. K. Ng
   33: #
   34: #init some globals
   35: $hidden::RANDOMINIT=0;
   36: $pi=atan2(1,1)*4;
   37: $rad2deg=180.0/$pi;
   38: $deg2rad=$pi/180.0;
   39: 
   40: sub caparesponse_check {
   41:   #not properly used yet: calc
   42:   #not to be used: $ans_fmt
   43:   my ($answer,$type,$tol,$sig,$ans_fmt,$unit,$calc,$samples) =
   44:     eval $_[1].
   45:       ';return ($answer,$type,$tol,$sig,$ans_fmt,$unit,$calc,$samples);';
   46: 
   47:   my $tol_type=''; # gets it's value from whether tol has a % or not done
   48:   my $sig_lbound=''; #done
   49:   my $sig_ubound=''; #done
   50:   my ($response,$expr)=@_;
   51: 
   52: 
   53:   #type's definitons come from capaParser.h
   54:   my $message='';
   55:   #remove leading and trailing whitespace
   56:   if ($response=~ /^\s|\s$/) {
   57:     $response=~ s:^\s+|\s+$::g;
   58:     $message .="Removed ws now :$response:<br />";
   59:   } else {
   60:     $message .="no ws in :$response:<br />";
   61:   }
   62: 
   63:   if ($type eq '' ) {
   64:     $message .= "Didn't find a type :$type:$expr: defaulting<br />";
   65:     if ( $answer eq ($answer *1.0)) { $type = 2;
   66:     } else { $type = 3; }
   67:   } else {
   68:          if ($type eq 'cs')    { $type = 4;
   69:     } elsif ($type eq 'ci')    { $type = 3;
   70:     } elsif ($type eq 'mc')    { $type = 5;
   71:     } elsif ($type eq 'fml')   { $type = 8;
   72:     } elsif ($type eq 'subj')  { $type = 7;
   73:     } elsif ($type eq 'float') { $type = 2;
   74:     } elsif ($type eq 'int')   { $type = 1;
   75:     } else { return "ERROR: Unknown type of answer: $type" }
   76:   }
   77: 
   78:   my $points;
   79:   my $id_list;
   80:   #formula type setup the sample points
   81:   if ($type eq '8') {
   82:     ($id_list,$points)=split(/@/,$samples);
   83:     $message.="Found :$points: points<br />";
   84:   }
   85:   if ($tol eq '') {
   86:     $tol=0.0;
   87:     $tol_type=1; #TOL_ABSOLUTE
   88:   } else {
   89:     if ($tol =~ /%$/) {
   90:       chop $tol;
   91:       $tol_type=2; #TOL_PERCENTAGE
   92:     } else {
   93:       $tol_type=1; #TOL_ABSOLUTE
   94:     }
   95:   }
   96: 
   97:   if ($sig eq '') {
   98:     $sig_lbound = 0; #SIG_LB_DEFAULT
   99:     $sig_ubound =15; #SIG_UB_DEFAULT
  100:   } else {
  101:     ($sig_lbound,$sig_ubound) = split /,/,$sig;
  102:   }
  103:   my $result = &caparesponse_capa_check_answer($response,$answer,$type,
  104: 					       $tol_type,$tol,
  105: 					       $sig_lbound,$sig_ubound,
  106: 					       $ans_fmt,$unit,$calc,$id_list,
  107: 					       $points,$external::randomseed);
  108: 
  109:   if    ($result == '1') { $result='EXACT_ANS'; } 
  110:   elsif ($result == '2') { $result='APPROX_ANS'; }
  111:   elsif ($result == '3') { $result='SIG_FAIL'; }
  112:   elsif ($result == '4') { $result='UNIT_FAIL'; }
  113:   elsif ($result == '5') { $result='NO_UNIT'; }
  114:   elsif ($result == '6') { $result='UNIT_OK'; }
  115:   elsif ($result == '7') { $result='INCORRECT'; }
  116:   elsif ($result == '8') { $result='UNIT_NOTNEEDED'; }
  117:   elsif ($result == '9') { $result='ANS_CNT_NOT_MATCH'; }
  118:   elsif ($result =='10') { $result='SUB_RECORDED'; }
  119:   elsif ($result =='11') { $result='BAD_FORMULA'; }
  120:   elsif ($result =='12') { $result='WANTED_NUMERIC'; }
  121:   else  {$result = "ERROR: Unknown Result:$result:$@:";}
  122: 
  123:   return "$result:<br />Error $error:<br />Answer $answer:<br />Response $response:<br /> type-$type|$tol|$tol_type|$sig:$sig_lbound:$sig_ubound|$unit|<br />$message$expr";
  124: }
  125: 
  126: sub get_array_args {
  127:   my ($expr,$arg)=@_;
  128:   # do these first, because who knows what varname the instructor might have used
  129:   # but it probably isn't $CAPARESPONSE_CHECK_LIST_answer
  130:   my $CAPARESPONSE_CHECK_LIST_answer = eval $expr.';return $'.$arg; #'
  131:   my $GET_ARRAY_ARGS_result;
  132:   my @GET_ARRAY_ARGS_list;
  133:   if ($CAPARESPONSE_CHECK_LIST_answer =~ /^\s*[\$\@]/) {
  134:     (@GET_ARRAY_ARGS_list) = eval $CAPARESPONSE_CHECK_LIST_answer;
  135:   }
  136:   $GET_ARRAY_ARGS_result.="error:$@:<br />";
  137:   # if the eval fails just use what is in the answer exactly
  138:   if (!defined(@GET_ARRAY_ARGS_list) || !defined($GET_ARRAY_ARGS_list[0])) {
  139:     $GET_ARRAY_ARGS_result.="list zero is undefined<br />";
  140:     $GET_ARRAY_ARGS_list[0]=$CAPARESPONSE_CHECK_LIST_answer;
  141:   }
  142:   return $GET_ARRAY_ARGS_result,@GET_ARRAY_ARGS_list;
  143: }
  144: 
  145: sub caparesponse_check_list {
  146:   my ($response,$expr)=@_;
  147:   my $result;
  148:   my ($result,@list) = &get_array_args($expr,'answer');
  149:   my $aresult='';
  150:   my $current_answer;
  151:   my $answers=join(':',@list);
  152:   $result.="Got response :$answers:<br />";
  153:   my @responselist;
  154:   my $type =eval $expr.';return $answer;';
  155:   if ($type ne '' && $#list > 0) {
  156:     (@responselist)=split /,/,$response;
  157:   } else {
  158:     (@responselist)=($response);
  159:   }
  160:   my $unit='';
  161:   $result.="Initial final response :$responselist['-1']:<br />";
  162:   if ($type eq '') {
  163:     #for numerical problems split off the unit
  164:     if ( $responselist['-1']=~ /(.*[^\s])\s+([^\s]+)/ ) {
  165:       $responselist['-1']=$1;
  166:       $unit=$2;
  167:     }
  168:   }
  169:   $result.="Final final response :$responselist['-1']:<br />";
  170:   $result.=":$#list: answers<br />";
  171:   $unit=~s/\s//;
  172:   my $i=0;
  173:   my $awards='';
  174:   for ($i=0; $i<@list;$i++) {
  175:     $result.="trying answer :$list[$i]:<br />";
  176:     if ($unit eq '') {
  177:       $aresult=&caparesponse_check($responselist[$i],
  178: 			     $expr.';my $answer=\''.$list[$i].'\';');
  179:     } else {
  180:       $aresult=&caparesponse_check($responselist[$i]." $unit",
  181: 				   $expr.';my $answer=\''.$list[$i].'\';');
  182:     }
  183:     my ($temp)=split /:/, $aresult;
  184:     $awards.="$temp,";
  185:     $result.=$aresult;
  186:   }
  187:   chop $awards;
  188:   return "$awards:<br />$result";
  189: }
  190: 
  191: sub tex {
  192:   if ( $external::target eq "tex" ) {
  193:     return @_[0];
  194:   } else {
  195:     return @_[1];
  196:   }
  197: }
  198: 
  199: sub var_in_tex {
  200:   if ( $external::target eq "tex" ) {
  201:     return @_[0];
  202:   } else {
  203:     return "";
  204:   }
  205: }
  206: 
  207: sub web {
  208:   if ( $external::target eq "tex" ) {
  209:     return @_[1];
  210:   } else {
  211:     if ( $external::target eq "web" || $external::target eq "answer") {
  212:       return @_[2];
  213:     } else {
  214:       return @_[0];
  215:     }
  216:   }
  217: }
  218: 
  219: sub html {
  220:   if ( $external::target eq "web" ) {
  221:     return shift;
  222:   }
  223: }
  224: 
  225: sub problem {
  226:   return '1';
  227: }
  228: 
  229: sub hinton {
  230:   return 0;
  231: }
  232: 
  233: sub random {
  234:   my ($start,$end,$step)=@_;
  235:   if ( ! $hidden::RANDOMINIT ) {
  236:     srand($external::randomseed);
  237:     $hidden::RANDOMINIT=1;
  238:   }
  239:   my $num=1+int(($end-$start)/$step);
  240:   my $result=$start + int(rand() * $num)*$step;
  241:   return $result;
  242: }
  243: 
  244: sub random_normal {
  245:   my ($item_cnt,$seed,$av,$std_dev) = @_;
  246:   my @retArray;
  247:   &random_set_seed_from_phrase($seed);
  248:   @retArray=&math_random_normal($item_cnt,$av,$std_dev);
  249:   return @retArray;
  250: }
  251: 
  252: sub random_beta {
  253:   my ($item_cnt,$seed,$aa,$bb) = @_;
  254:   my @retArray;
  255:   &random_set_seed_from_phrase($seed);
  256:   @retArray=&math_random_beta($item_cnt,$aa,$bb);
  257:   return @retArray;
  258: }
  259: 
  260: sub random_gamma {
  261:   my ($item_cnt,$seed,$a,$r) = @_;
  262:   my @retArray;
  263:   &random_set_seed_from_phrase($seed);
  264:   @retArray=&math_random_gamma($item_cnt,$a,$r);
  265:   return @retArray;
  266: }
  267: 
  268: sub random_exponential {
  269:   my ($item_cnt,$seed,$av) = @_;
  270:   my @retArray;
  271:   &random_set_seed_from_phrase($seed);
  272:   @retArray=&math_random_exponential($item_cnt,$av);
  273:   return @retArray;
  274: }
  275: 
  276: sub random_poisson {
  277:   my ($item_cnt,$seed,$mu) = @_;
  278:   my @retArray;
  279:   &random_set_seed_from_phrase($seed);
  280:   @retArray=&math_random_poisson($item_cnt,$mu);
  281:   return @retArray;
  282: }
  283: 
  284: sub random_chi {
  285:   my ($item_cnt,$seed,$df) = @_;
  286:   my @retArray;
  287:   &random_set_seed_from_phrase($seed);
  288:   @retArray=&math_random_chi_square($item_cnt,$df);
  289:   return @retArray;
  290: }
  291: 
  292: sub random_noncentral_chi {
  293:   my ($item_cnt,$seed,$df,$nonc) = @_;
  294:   my @retArray;
  295:   &random_set_seed_from_phrase($seed);
  296:   @retArray=&math_random_noncentral_chi_square($item_cnt,$df,$nonc);
  297:   return @retArray;
  298: }
  299: 
  300: sub random_f {
  301:   my ($item_cnt,$seed,$dfn,$dfd) = @_;
  302:   my @retArray;
  303:   &random_set_seed_from_phrase($seed);
  304:   @retArray=&math_random_f($item_cnt,$dfn,$dfd);
  305:   return @retArray;
  306: }
  307: 
  308: sub random_noncentral_f {
  309:   my ($item_cnt,$seed,$dfn,$dfd,$nonc) = @_;
  310:   my @retArray;
  311:   &random_set_seed_from_phrase($seed);
  312:   @retArray=&math_random_noncentral_f($item_cnt,$dfn,$dfd,$nonc);
  313:   return @retArray;
  314: }
  315: 
  316: sub random_multivariate_normal {
  317:   my ($item_cnt,$seed,$mean,$covar) = @_;
  318:   &random_set_seed_from_phrase($seed);
  319:   @retArray=&math_random_multivariate_normal($item_cnt,@$mean,@$covar);
  320:   return @retArray;
  321: }
  322: 
  323: sub random_multinomial {
  324:   my ($item_cnt,$seed,@p) = @_;
  325:   my @retArray;
  326:   &random_set_seed_from_phrase($seed);
  327:   @retArray=&math_random_multinomial($item_cnt,@p);
  328:   return @retArray;
  329: }
  330: 
  331: sub random_permutation {
  332:   my ($seed,@inArray) = @_;
  333:   my @retArray;
  334:   &random_set_seed_from_phrase($seed);
  335:   @retArray=&math_random_permutation(@inArray);
  336:   return @retArray;
  337: }
  338: 
  339: sub random_uniform {
  340:   my ($item_cnt,$seed,$low,$high) = @_;
  341:   my @retArray;
  342:   &random_set_seed_from_phrase($seed);
  343:   @retArray=&math_random_uniform($item_cnt,$low,$high);
  344:   return @retArray;
  345: }
  346: 
  347: sub random_uniform_integer {
  348:   my ($item_cnt,$seed,$low,$high) = @_;
  349:   my @retArray;
  350:   &random_set_seed_from_phrase($seed);
  351:   @retArray=&math_random_uniform_integer($item_cnt,$low,$high);
  352:   return @retArray;
  353: }
  354: 
  355: sub random_binomial {
  356:   my ($item_cnt,$seed,$nt,$p) = @_;
  357:   my @retArray;
  358:   &random_set_seed_from_phrase($seed);
  359:   @retArray=&math_random_binomial($item_cnt,$nt,$p);
  360:   return @retArray;
  361: }
  362: 
  363: sub random_negative_binomial {
  364:   my ($item_cnt,$seed,$ne,$p) = @_;
  365:   my @retArray;
  366:   &random_set_seed_from_phrase($seed);
  367:   @retArray=&math_random_negative_binomial($item_cnt,$ne,$p);
  368:   return @retArray;
  369: }
  370: 
  371: sub abs { abs(shift) }
  372: sub sin { sin(shift) }
  373: sub cos { cos(shift) }
  374: sub exp { exp(shift) }
  375: sub int { int(shift) }
  376: sub log { log(shift) }
  377: sub atan2 { atan2($_[0],$_[1]) }
  378: sub sqrt { sqrt(shift) }
  379: 
  380: sub tan  { sin($_[0]) / cos($_[0]) }
  381: #sub atan { atan2($_[0], 1); }
  382: #sub acos { atan2(sqrt(1 - $_[0] * $_[0]), $_[0] ); }
  383: #sub asin { atan2($_[0], sqrt(1- $_[0] * $_[0]) );  }
  384: 
  385: sub log10 { log($_[0])/log(10); }
  386: 
  387: sub factorial {
  388:     my $input = int(shift);
  389:     return "Error - unable to take factorial of an negative number ($input)" if $input < 0;
  390:     return "Error - factorial result is greater than system limit ($input)" if $input > 170;
  391:     return 1 if $input == 0;
  392:     my $result = 1; 
  393:     for (my $i=2; $i<=$input; $i++) { $result *= $i }
  394:     return $result;
  395: }
  396: 
  397: sub sgn {
  398:     return -1 if $_[0] < 0;
  399:     return 0 if $_[0] == 0;
  400:     return 1 if $_[0] > 0;
  401: }
  402: 
  403: sub min {
  404:     my @sorted = sort { $a <=> $b || $a cmp $b } @_;
  405:     return shift @sorted;
  406: }
  407: 
  408: sub max {
  409:     my @sorted = sort { $a <=> $b || $a cmp $b } @_;
  410:     return pop @sorted;
  411: }
  412: 
  413: sub roundto {
  414:     my ($input,$n) = @_;
  415:     return sprintf('%.'.$n.'f',$input);
  416: }
  417: 
  418: sub to_string {
  419:     my ($input,$n) = @_;
  420:     return sprintf($input) if $n eq "";
  421:     $n = '.'.$n if $n !~ /^\./;
  422:     return sprintf('%'.$n,$input) if $n ne "";
  423: }
  424: 
  425: sub sub_string {
  426:     my ($str,$start,$len) = @_;
  427:     return substr($str,$start-1,$len);
  428: }
  429: 
  430: sub pow   {return $_[0] ** $_[1]; }
  431: sub ceil  {return (($_[0]-int($_[0]))== 0.0) ? $_[0] : (($_[0] > 0) ? (int($_[0])+ 1) : int($_[0])); }
  432: sub floor  {return (($_[0]-int($_[0]))== 0.0) ? $_[0] : (($_[0] > 0) ? int($_[0]) : (int($_[0])-1)); }
  433: #sub floor {return int($_[0]); }
  434: 
  435: sub format {
  436:   my ($value,$fmt)=@_;
  437:   return sprintf('%.'.$fmt,$value);
  438: }
  439: 
  440: sub map {
  441:     my ($phrase,$dest,$source)=@_;
  442:     my @seed = &random_seed_from_phrase($phrase);
  443:     &random_set_seed(@seed);
  444:     my $destct = scalar(@$dest);
  445:     if (!$source) {
  446: 	my @output;
  447: 	my @idx = &math_random_permuted_index($destct);
  448: 	my $ctr = 0;
  449: 	while ($ctr < $destct) {
  450: 	    $output[$ctr] = $$dest[$idx[$ctr]];
  451: 	    $ctr++;
  452: 	}
  453: 	return @output;
  454:     } else {
  455: 	my $num = scalar(@$source);
  456: 	my @idx = &math_random_permuted_index($num);
  457: 	my $ctr = 0;
  458: 	my $tot = $num;
  459: 	$tot = $destct if $destct < $num;
  460: 	if (ref($$dest[0])) {
  461: 	    while ($ctr < $tot) {
  462: 		${$$dest[$ctr]} = $$source[$idx[$ctr]];
  463: 	        $ctr++;
  464:             }
  465:         } else {
  466: 	    while ($ctr < $tot) {
  467: 		$$dest[$ctr] = $$source[$idx[$ctr]];
  468: 		$ctr++;
  469: 	    }
  470: 	}
  471:     }
  472: }
  473: 
  474: sub rmap {
  475:     my ($phrase,$dest,$source)=@_;
  476:     my @seed = &random_seed_from_phrase($phrase);
  477:     &random_set_seed(@seed);
  478:     my $destct = scalar(@$dest);
  479:     if (!$source) {
  480: 	my @idx = &math_random_permuted_index($destct);
  481: 	my $ctr = 0;
  482: 	my @r_idx;
  483: 	while ($ctr < $destct) {
  484: 	    $r_idx[$idx[$ctr]] = $ctr;
  485: 	    $ctr++;
  486: 	}
  487: 	my @output;
  488: 	$ctr = 0;
  489: 	while ($ctr < $destct) {
  490: 	    $output[$ctr] = $$dest[$r_idx[$ctr]];
  491: 	    $ctr++;
  492: 	}
  493: 	return @output;
  494:     } else {
  495: 	my $num = scalar(@$source);
  496: 	my @idx = &math_random_permuted_index($num);
  497: 	my $ctr = 0;
  498: 	my $tot = $num;
  499: 	$tot = $destct if $destct < $num;
  500: 	my @r_idx;
  501: 	while ($ctr < $tot) {
  502: 	    $r_idx[$idx[$ctr]] = $ctr;
  503: 	    $ctr++;
  504: 	}
  505: 	$ctr = 0;
  506: 	if (ref($$dest[0])) {
  507: 	    while ($ctr < $tot) {
  508: 		${$$dest[$ctr]} = $$source[$r_idx[$ctr]];
  509: 	        $ctr++;
  510:             }
  511:         } else {
  512: 	    while ($ctr < $tot) {
  513: 		$$dest[$ctr] = $$source[$r_idx[$ctr]];
  514: 		$ctr++;
  515: 	    }
  516: 	}
  517:     }
  518: }
  519: 
  520: sub capa_id { return }
  521: 
  522: sub problem { return }
  523: 
  524: sub name{
  525:   my $fullname = &EXT('environment.lastname').', '.&EXT('environment.firstname').' '.&EXT('environment.middlename');
  526:   $fullname = "" if $fullname eq ",  ";
  527:   $fullname =~ s/\%2d/-/g;
  528:   return $fullname;
  529: }
  530: 
  531: sub student_number { 
  532:   my $id = &EXT('environment.id');
  533:   $id = '' if $id eq "";
  534:   return $id;
  535: }
  536: 
  537: sub class {
  538:   my $course = &EXT('course.description');
  539:   $course = '' if $course eq "";
  540:   return $course;
  541: }
  542: 
  543: sub sec { 
  544:   my $sec = &EXT('request.course.sec');
  545:   $sec = '' if $sec eq "";
  546:   return $sec;
  547: }
  548: 
  549: sub open_date { 
  550:   my @dc = split(/\s+/,localtime(&EXT('resource.0.opendate')));
  551:   return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
  552:   my @hm = split(/:/,$dc[3]);
  553:   my $ampm = " am";
  554:   if ($hm[0] > 12) {
  555:     $hm[0]-=12;
  556:     $ampm = " pm";
  557:   }
  558:   return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
  559: }
  560: 
  561: sub due_date { 
  562:   my @dc = split(/\s+/,localtime(&EXT('resource.0.duedate')));
  563:   return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
  564:   my @hm = split(/:/,$dc[3]);
  565:   my $ampm = " am";
  566:   if ($hm[0] > 12) {
  567:     $hm[0]-=12;
  568:     $ampm = " pm";
  569:   }
  570:   return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
  571: #  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$dc[3];
  572: }
  573: 
  574: sub answer_date { 
  575:   my @dc = split(/\s+/,localtime(&EXT('resource.0.answerdate')));
  576:   return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
  577:   my @hm = split(/:/,$dc[3]);
  578:   my $ampm = " am";
  579:   if ($hm[0] > 12) {
  580:     $hm[0]-=12;
  581:     $ampm = " pm";
  582:   }
  583:   return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
  584: #  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$dc[3];
  585: }
  586: 
  587: sub array_moments {
  588:   my @input=@_;
  589:   my (@output,$N);
  590:   $N=scalar (@input);
  591:   $output[0]=$N;
  592:   if ($N <= 1) {
  593:     $output[1]=$input[0];
  594:     $output[1]="Input array not defined" if ($N == 0);
  595:     $output[2]="variance undefined for N<=1";
  596:     $output[3]="skewness undefined for N<=1";
  597:     $output[4]="kurtosis undefined for N<=1";
  598:     return @output;
  599:   }
  600:   my $sum=0;
  601:   foreach my $line (@input) {
  602:     $sum+=$line;
  603:   }
  604:   $output[1] = $sum/$N;
  605:   my ($x,$sdev,$var,$skew,$kurt) = 0;
  606:   foreach my $line (@input) {
  607:     $x=$line-$output[1];
  608:     $var+=$x**2;
  609:     $skew+=$x**3;
  610:     $kurt+=$x**4;
  611:   }
  612:   $output[2]=$var/($N-1);
  613:   $sdev=sqrt($output[2]);
  614:   if ($sdev == 0) {
  615:      $output[3]="inf-variance=0";
  616:      $output[4]="inf-variance=0";
  617:      return @output;
  618:   }
  619:   $output[3]=$skew/($sdev**3*$N);
  620:   $output[4]=$kurt/($sdev**4*$N)-3;
  621:   return @output;
  622: }
  623: 
  624: sub choose {
  625:   my $num = $_[0];
  626:   return $_[$num];
  627: }
  628: 
  629: 

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