File:  [LON-CAPA] / loncom / homework / default_homework.lcpm
Revision 1.44: download - view: text, annotated - select for diffs
Fri Dec 21 21:37:26 2001 UTC (22 years, 4 months ago) by matthew
Branches: MAIN
CVS tags: HEAD
Added missing internal variable $"

    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 1.44 2001/12/21 21:37:26 matthew 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: # 12/21/2001 Matthew
   34: #
   35: #init some globals
   36: $hidden::RANDOMINIT=0;
   37: $pi=atan2(1,1)*4;
   38: $rad2deg=180.0/$pi;
   39: $deg2rad=$pi/180.0;
   40: $"=' ';
   41: 
   42: sub caparesponse_check {
   43:   #not properly used yet: calc
   44:   #not to be used: $ans_fmt
   45:   my ($answer,$type,$tol,$sig,$ans_fmt,$unit,$calc,$samples) =
   46:     eval $_[1].
   47:       ';return ($answer,$type,$tol,$sig,$ans_fmt,$unit,$calc,$samples);';
   48: 
   49:   my $tol_type=''; # gets it's value from whether tol has a % or not done
   50:   my $sig_lbound=''; #done
   51:   my $sig_ubound=''; #done
   52:   my ($response,$expr)=@_;
   53: 
   54: 
   55:   #type's definitons come from capaParser.h
   56:   my $message='';
   57:   #remove leading and trailing whitespace
   58:   if ($response=~ /^\s|\s$/) {
   59:     $response=~ s:^\s+|\s+$::g;
   60:     $message .="Removed ws now :$response:<br />";
   61:   } else {
   62:     $message .="no ws in :$response:<br />";
   63:   }
   64: 
   65:   if ($type eq '' ) {
   66:     $message .= "Didn't find a type :$type:$expr: defaulting<br />";
   67:     if ( $answer eq ($answer *1.0)) { $type = 2;
   68:     } else { $type = 3; }
   69:   } else {
   70:          if ($type eq 'cs')    { $type = 4;
   71:     } elsif ($type eq 'ci')    { $type = 3;
   72:     } elsif ($type eq 'mc')    { $type = 5;
   73:     } elsif ($type eq 'fml')   { $type = 8;
   74:     } elsif ($type eq 'subj')  { $type = 7;
   75:     } elsif ($type eq 'float') { $type = 2;
   76:     } elsif ($type eq 'int')   { $type = 1;
   77:     } else { return "ERROR: Unknown type of answer: $type" }
   78:   }
   79: 
   80:   my $points;
   81:   my $id_list;
   82:   #formula type setup the sample points
   83:   if ($type eq '8') {
   84:     ($id_list,$points)=split(/@/,$samples);
   85:     $message.="Found :$points: points<br />";
   86:   }
   87:   if ($tol eq '') {
   88:     $tol=0.0;
   89:     $tol_type=1; #TOL_ABSOLUTE
   90:   } else {
   91:     if ($tol =~ /%$/) {
   92:       chop $tol;
   93:       $tol_type=2; #TOL_PERCENTAGE
   94:     } else {
   95:       $tol_type=1; #TOL_ABSOLUTE
   96:     }
   97:   }
   98: 
   99:   if ($sig eq '') {
  100:     $sig_lbound = 0; #SIG_LB_DEFAULT
  101:     $sig_ubound =15; #SIG_UB_DEFAULT
  102:   } else {
  103:     ($sig_lbound,$sig_ubound) = split /,/,$sig;
  104:   }
  105:   my $result = &caparesponse_capa_check_answer($response,$answer,$type,
  106: 					       $tol_type,$tol,
  107: 					       $sig_lbound,$sig_ubound,
  108: 					       $ans_fmt,$unit,$calc,$id_list,
  109: 					       $points,$external::randomseed);
  110: 
  111:   if    ($result == '1') { $result='EXACT_ANS'; } 
  112:   elsif ($result == '2') { $result='APPROX_ANS'; }
  113:   elsif ($result == '3') { $result='SIG_FAIL'; }
  114:   elsif ($result == '4') { $result='UNIT_FAIL'; }
  115:   elsif ($result == '5') { $result='NO_UNIT'; }
  116:   elsif ($result == '6') { $result='UNIT_OK'; }
  117:   elsif ($result == '7') { $result='INCORRECT'; }
  118:   elsif ($result == '8') { $result='UNIT_NOTNEEDED'; }
  119:   elsif ($result == '9') { $result='ANS_CNT_NOT_MATCH'; }
  120:   elsif ($result =='10') { $result='SUB_RECORDED'; }
  121:   elsif ($result =='11') { $result='BAD_FORMULA'; }
  122:   elsif ($result =='12') { $result='WANTED_NUMERIC'; }
  123:   else  {$result = "ERROR: Unknown Result:$result:$@:";}
  124: 
  125:   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";
  126: }
  127: 
  128: sub get_array_args {
  129:   my ($expr,$arg)=@_;
  130:   # do these first, because who knows what varname the instructor might have used
  131:   # but it probably isn't $CAPARESPONSE_CHECK_LIST_answer
  132:   my $CAPARESPONSE_CHECK_LIST_answer = eval $expr.';return $'.$arg; #'
  133:   my $GET_ARRAY_ARGS_result;
  134:   my @GET_ARRAY_ARGS_list;
  135:   if ($CAPARESPONSE_CHECK_LIST_answer =~ /^\s*[\$\@]/) {
  136:     (@GET_ARRAY_ARGS_list) = eval $CAPARESPONSE_CHECK_LIST_answer;
  137:   }
  138:   $GET_ARRAY_ARGS_result.="error:$@:<br />";
  139:   # if the eval fails just use what is in the answer exactly
  140:   if (!defined(@GET_ARRAY_ARGS_list) || !defined($GET_ARRAY_ARGS_list[0])) {
  141:     $GET_ARRAY_ARGS_result.="list zero is undefined<br />";
  142:     $GET_ARRAY_ARGS_list[0]=$CAPARESPONSE_CHECK_LIST_answer;
  143:   }
  144:   return $GET_ARRAY_ARGS_result,@GET_ARRAY_ARGS_list;
  145: }
  146: 
  147: sub caparesponse_check_list {
  148:   my ($response,$expr)=@_;
  149:   my $result;
  150:   my ($result,@list) = &get_array_args($expr,'answer');
  151:   my $aresult='';
  152:   my $current_answer;
  153:   my $answers=join(':',@list);
  154:   $result.="Got response :$answers:<br />";
  155:   my @responselist;
  156:   my $type =eval $expr.';return $answer;';
  157:   if ($type ne '' && $#list > 0) {
  158:     (@responselist)=split /,/,$response;
  159:   } else {
  160:     (@responselist)=($response);
  161:   }
  162:   my $unit='';
  163:   $result.="Initial final response :$responselist['-1']:<br />";
  164:   if ($type eq '') {
  165:     #for numerical problems split off the unit
  166:     if ( $responselist['-1']=~ /(.*[^\s])\s+([^\s]+)/ ) {
  167:       $responselist['-1']=$1;
  168:       $unit=$2;
  169:     }
  170:   }
  171:   $result.="Final final response :$responselist['-1']:<br />";
  172:   $result.=":$#list: answers<br />";
  173:   $unit=~s/\s//;
  174:   my $i=0;
  175:   my $awards='';
  176:   for ($i=0; $i<@list;$i++) {
  177:     $result.="trying answer :$list[$i]:<br />";
  178:     if ($unit eq '') {
  179:       $aresult=&caparesponse_check($responselist[$i],
  180: 			     $expr.';my $answer=\''.$list[$i].'\';');
  181:     } else {
  182:       $aresult=&caparesponse_check($responselist[$i]." $unit",
  183: 				   $expr.';my $answer=\''.$list[$i].'\';');
  184:     }
  185:     my ($temp)=split /:/, $aresult;
  186:     $awards.="$temp,";
  187:     $result.=$aresult;
  188:   }
  189:   chop $awards;
  190:   return "$awards:<br />$result";
  191: }
  192: 
  193: sub tex {
  194:   if ( $external::target eq "tex" ) {
  195:     return @_[0];
  196:   } else {
  197:     return @_[1];
  198:   }
  199: }
  200: 
  201: sub var_in_tex {
  202:   if ( $external::target eq "tex" ) {
  203:     return @_[0];
  204:   } else {
  205:     return "";
  206:   }
  207: }
  208: 
  209: sub web {
  210:   if ( $external::target eq "tex" ) {
  211:     return @_[1];
  212:   } else {
  213:     if ( $external::target eq "web" || $external::target eq "answer") {
  214:       return @_[2];
  215:     } else {
  216:       return @_[0];
  217:     }
  218:   }
  219: }
  220: 
  221: sub html {
  222:   if ( $external::target eq "web" ) {
  223:     return shift;
  224:   }
  225: }
  226: 
  227: sub problem {
  228:   return '1';
  229: }
  230: 
  231: sub hinton {
  232:   return 0;
  233: }
  234: 
  235: sub random {
  236:   my ($start,$end,$step)=@_;
  237:   if ( ! $hidden::RANDOMINIT ) {
  238:     srand($external::randomseed);
  239:     $hidden::RANDOMINIT=1;
  240:   }
  241:   my $num=1+int(($end-$start)/$step);
  242:   my $result=$start + int(rand() * $num)*$step;
  243:   return $result;
  244: }
  245: 
  246: sub random_normal {
  247:   my ($item_cnt,$seed,$av,$std_dev) = @_;
  248:   my @retArray;
  249:   &random_set_seed_from_phrase($seed);
  250:   @retArray=&math_random_normal($item_cnt,$av,$std_dev);
  251:   return @retArray;
  252: }
  253: 
  254: sub random_beta {
  255:   my ($item_cnt,$seed,$aa,$bb) = @_;
  256:   my @retArray;
  257:   &random_set_seed_from_phrase($seed);
  258:   @retArray=&math_random_beta($item_cnt,$aa,$bb);
  259:   return @retArray;
  260: }
  261: 
  262: sub random_gamma {
  263:   my ($item_cnt,$seed,$a,$r) = @_;
  264:   my @retArray;
  265:   &random_set_seed_from_phrase($seed);
  266:   @retArray=&math_random_gamma($item_cnt,$a,$r);
  267:   return @retArray;
  268: }
  269: 
  270: sub random_exponential {
  271:   my ($item_cnt,$seed,$av) = @_;
  272:   my @retArray;
  273:   &random_set_seed_from_phrase($seed);
  274:   @retArray=&math_random_exponential($item_cnt,$av);
  275:   return @retArray;
  276: }
  277: 
  278: sub random_poisson {
  279:   my ($item_cnt,$seed,$mu) = @_;
  280:   my @retArray;
  281:   &random_set_seed_from_phrase($seed);
  282:   @retArray=&math_random_poisson($item_cnt,$mu);
  283:   return @retArray;
  284: }
  285: 
  286: sub random_chi {
  287:   my ($item_cnt,$seed,$df) = @_;
  288:   my @retArray;
  289:   &random_set_seed_from_phrase($seed);
  290:   @retArray=&math_random_chi_square($item_cnt,$df);
  291:   return @retArray;
  292: }
  293: 
  294: sub random_noncentral_chi {
  295:   my ($item_cnt,$seed,$df,$nonc) = @_;
  296:   my @retArray;
  297:   &random_set_seed_from_phrase($seed);
  298:   @retArray=&math_random_noncentral_chi_square($item_cnt,$df,$nonc);
  299:   return @retArray;
  300: }
  301: 
  302: sub random_f {
  303:   my ($item_cnt,$seed,$dfn,$dfd) = @_;
  304:   my @retArray;
  305:   &random_set_seed_from_phrase($seed);
  306:   @retArray=&math_random_f($item_cnt,$dfn,$dfd);
  307:   return @retArray;
  308: }
  309: 
  310: sub random_noncentral_f {
  311:   my ($item_cnt,$seed,$dfn,$dfd,$nonc) = @_;
  312:   my @retArray;
  313:   &random_set_seed_from_phrase($seed);
  314:   @retArray=&math_random_noncentral_f($item_cnt,$dfn,$dfd,$nonc);
  315:   return @retArray;
  316: }
  317: 
  318: sub random_multivariate_normal {
  319:   my ($item_cnt,$seed,$mean,$covar) = @_;
  320:   &random_set_seed_from_phrase($seed);
  321:   @retArray=&math_random_multivariate_normal($item_cnt,@$mean,@$covar);
  322:   return @retArray;
  323: }
  324: 
  325: sub random_multinomial {
  326:   my ($item_cnt,$seed,@p) = @_;
  327:   my @retArray;
  328:   &random_set_seed_from_phrase($seed);
  329:   @retArray=&math_random_multinomial($item_cnt,@p);
  330:   return @retArray;
  331: }
  332: 
  333: sub random_permutation {
  334:   my ($seed,@inArray) = @_;
  335:   my @retArray;
  336:   &random_set_seed_from_phrase($seed);
  337:   @retArray=&math_random_permutation(@inArray);
  338:   return @retArray;
  339: }
  340: 
  341: sub random_uniform {
  342:   my ($item_cnt,$seed,$low,$high) = @_;
  343:   my @retArray;
  344:   &random_set_seed_from_phrase($seed);
  345:   @retArray=&math_random_uniform($item_cnt,$low,$high);
  346:   return @retArray;
  347: }
  348: 
  349: sub random_uniform_integer {
  350:   my ($item_cnt,$seed,$low,$high) = @_;
  351:   my @retArray;
  352:   &random_set_seed_from_phrase($seed);
  353:   @retArray=&math_random_uniform_integer($item_cnt,$low,$high);
  354:   return @retArray;
  355: }
  356: 
  357: sub random_binomial {
  358:   my ($item_cnt,$seed,$nt,$p) = @_;
  359:   my @retArray;
  360:   &random_set_seed_from_phrase($seed);
  361:   @retArray=&math_random_binomial($item_cnt,$nt,$p);
  362:   return @retArray;
  363: }
  364: 
  365: sub random_negative_binomial {
  366:   my ($item_cnt,$seed,$ne,$p) = @_;
  367:   my @retArray;
  368:   &random_set_seed_from_phrase($seed);
  369:   @retArray=&math_random_negative_binomial($item_cnt,$ne,$p);
  370:   return @retArray;
  371: }
  372: 
  373: sub abs { abs(shift) }
  374: sub sin { sin(shift) }
  375: sub cos { cos(shift) }
  376: sub exp { exp(shift) }
  377: sub int { int(shift) }
  378: sub log { log(shift) }
  379: sub atan2 { atan2($_[0],$_[1]) }
  380: sub sqrt { sqrt(shift) }
  381: 
  382: sub tan  { sin($_[0]) / cos($_[0]) }
  383: #sub atan { atan2($_[0], 1); }
  384: #sub acos { atan2(sqrt(1 - $_[0] * $_[0]), $_[0] ); }
  385: #sub asin { atan2($_[0], sqrt(1- $_[0] * $_[0]) );  }
  386: 
  387: sub log10 { log($_[0])/log(10); }
  388: 
  389: sub factorial {
  390:     my $input = int(shift);
  391:     return "Error - unable to take factorial of an negative number ($input)" if $input < 0;
  392:     return "Error - factorial result is greater than system limit ($input)" if $input > 170;
  393:     return 1 if $input == 0;
  394:     my $result = 1; 
  395:     for (my $i=2; $i<=$input; $i++) { $result *= $i }
  396:     return $result;
  397: }
  398: 
  399: sub sgn {
  400:     return -1 if $_[0] < 0;
  401:     return 0 if $_[0] == 0;
  402:     return 1 if $_[0] > 0;
  403: }
  404: 
  405: sub min {
  406:     my @sorted = sort { $a <=> $b || $a cmp $b } @_;
  407:     return shift @sorted;
  408: }
  409: 
  410: sub max {
  411:     my @sorted = sort { $a <=> $b || $a cmp $b } @_;
  412:     return pop @sorted;
  413: }
  414: 
  415: sub roundto {
  416:     my ($input,$n) = @_;
  417:     return sprintf('%.'.$n.'f',$input);
  418: }
  419: 
  420: sub to_string {
  421:     my ($input,$n) = @_;
  422:     return sprintf($input) if $n eq "";
  423:     $n = '.'.$n if $n !~ /^\./;
  424:     return sprintf('%'.$n,$input) if $n ne "";
  425: }
  426: 
  427: sub sub_string {
  428:     my ($str,$start,$len) = @_;
  429:     return substr($str,$start-1,$len);
  430: }
  431: 
  432: sub pow   {return $_[0] ** $_[1]; }
  433: sub ceil  {return (($_[0]-int($_[0]))== 0.0) ? $_[0] : (($_[0] > 0) ? (int($_[0])+ 1) : int($_[0])); }
  434: sub floor  {return (($_[0]-int($_[0]))== 0.0) ? $_[0] : (($_[0] > 0) ? int($_[0]) : (int($_[0])-1)); }
  435: #sub floor {return int($_[0]); }
  436: 
  437: sub format {
  438:   my ($value,$fmt)=@_;
  439:   return sprintf('%.'.$fmt,$value);
  440: }
  441: 
  442: sub map {
  443:     my ($phrase,$dest,$source)=@_;
  444:     my @seed = &random_seed_from_phrase($phrase);
  445:     &random_set_seed(@seed);
  446:     my $destct = scalar(@$dest);
  447:     if (!$source) {
  448: 	my @output;
  449: 	my @idx = &math_random_permuted_index($destct);
  450: 	my $ctr = 0;
  451: 	while ($ctr < $destct) {
  452: 	    $output[$ctr] = $$dest[$idx[$ctr]];
  453: 	    $ctr++;
  454: 	}
  455: 	return @output;
  456:     } else {
  457: 	my $num = scalar(@$source);
  458: 	my @idx = &math_random_permuted_index($num);
  459: 	my $ctr = 0;
  460: 	my $tot = $num;
  461: 	$tot = $destct if $destct < $num;
  462: 	if (ref($$dest[0])) {
  463: 	    while ($ctr < $tot) {
  464: 		${$$dest[$ctr]} = $$source[$idx[$ctr]];
  465: 	        $ctr++;
  466:             }
  467:         } else {
  468: 	    while ($ctr < $tot) {
  469: 		$$dest[$ctr] = $$source[$idx[$ctr]];
  470: 		$ctr++;
  471: 	    }
  472: 	}
  473:     }
  474: }
  475: 
  476: sub rmap {
  477:     my ($phrase,$dest,$source)=@_;
  478:     my @seed = &random_seed_from_phrase($phrase);
  479:     &random_set_seed(@seed);
  480:     my $destct = scalar(@$dest);
  481:     if (!$source) {
  482: 	my @idx = &math_random_permuted_index($destct);
  483: 	my $ctr = 0;
  484: 	my @r_idx;
  485: 	while ($ctr < $destct) {
  486: 	    $r_idx[$idx[$ctr]] = $ctr;
  487: 	    $ctr++;
  488: 	}
  489: 	my @output;
  490: 	$ctr = 0;
  491: 	while ($ctr < $destct) {
  492: 	    $output[$ctr] = $$dest[$r_idx[$ctr]];
  493: 	    $ctr++;
  494: 	}
  495: 	return @output;
  496:     } else {
  497: 	my $num = scalar(@$source);
  498: 	my @idx = &math_random_permuted_index($num);
  499: 	my $ctr = 0;
  500: 	my $tot = $num;
  501: 	$tot = $destct if $destct < $num;
  502: 	my @r_idx;
  503: 	while ($ctr < $tot) {
  504: 	    $r_idx[$idx[$ctr]] = $ctr;
  505: 	    $ctr++;
  506: 	}
  507: 	$ctr = 0;
  508: 	if (ref($$dest[0])) {
  509: 	    while ($ctr < $tot) {
  510: 		${$$dest[$ctr]} = $$source[$r_idx[$ctr]];
  511: 	        $ctr++;
  512:             }
  513:         } else {
  514: 	    while ($ctr < $tot) {
  515: 		$$dest[$ctr] = $$source[$r_idx[$ctr]];
  516: 		$ctr++;
  517: 	    }
  518: 	}
  519:     }
  520: }
  521: 
  522: sub capa_id { return }
  523: 
  524: sub problem { return }
  525: 
  526: sub name{
  527:   my $fullname = &EXT('environment.lastname').', '.&EXT('environment.firstname').' '.&EXT('environment.middlename');
  528:   $fullname = "" if $fullname eq ",  ";
  529:   $fullname =~ s/\%2d/-/g;
  530:   return $fullname;
  531: }
  532: 
  533: sub student_number { 
  534:   my $id = &EXT('environment.id');
  535:   $id = '' if $id eq "";
  536:   return $id;
  537: }
  538: 
  539: sub class {
  540:   my $course = &EXT('course.description');
  541:   $course = '' if $course eq "";
  542:   return $course;
  543: }
  544: 
  545: sub sec { 
  546:   my $sec = &EXT('request.course.sec');
  547:   $sec = '' if $sec eq "";
  548:   return $sec;
  549: }
  550: 
  551: sub open_date { 
  552:   my @dc = split(/\s+/,localtime(&EXT('resource.0.opendate')));
  553:   return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
  554:   my @hm = split(/:/,$dc[3]);
  555:   my $ampm = " am";
  556:   if ($hm[0] > 12) {
  557:     $hm[0]-=12;
  558:     $ampm = " pm";
  559:   }
  560:   return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
  561: }
  562: 
  563: sub due_date { 
  564:   my @dc = split(/\s+/,localtime(&EXT('resource.0.duedate')));
  565:   return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
  566:   my @hm = split(/:/,$dc[3]);
  567:   my $ampm = " am";
  568:   if ($hm[0] > 12) {
  569:     $hm[0]-=12;
  570:     $ampm = " pm";
  571:   }
  572:   return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
  573: #  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$dc[3];
  574: }
  575: 
  576: sub answer_date { 
  577:   my @dc = split(/\s+/,localtime(&EXT('resource.0.answerdate')));
  578:   return '' if ($dc[0] eq "Wed" and $dc[2] == 31 and $dc[4] == 1969);
  579:   my @hm = split(/:/,$dc[3]);
  580:   my $ampm = " am";
  581:   if ($hm[0] > 12) {
  582:     $hm[0]-=12;
  583:     $ampm = " pm";
  584:   }
  585:   return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$hm[0].':'.$hm[1].$ampm;
  586: #  return $dc[0].', '.$dc[1].' '.$dc[2].', '.$dc[4].' at '.$dc[3];
  587: }
  588: 
  589: sub array_moments {
  590:   my @input=@_;
  591:   my (@output,$N);
  592:   $N=scalar (@input);
  593:   $output[0]=$N;
  594:   if ($N <= 1) {
  595:     $output[1]=$input[0];
  596:     $output[1]="Input array not defined" if ($N == 0);
  597:     $output[2]="variance undefined for N<=1";
  598:     $output[3]="skewness undefined for N<=1";
  599:     $output[4]="kurtosis undefined for N<=1";
  600:     return @output;
  601:   }
  602:   my $sum=0;
  603:   foreach my $line (@input) {
  604:     $sum+=$line;
  605:   }
  606:   $output[1] = $sum/$N;
  607:   my ($x,$sdev,$var,$skew,$kurt) = 0;
  608:   foreach my $line (@input) {
  609:     $x=$line-$output[1];
  610:     $var+=$x**2;
  611:     $skew+=$x**3;
  612:     $kurt+=$x**4;
  613:   }
  614:   $output[2]=$var/($N-1);
  615:   $sdev=sqrt($output[2]);
  616:   if ($sdev == 0) {
  617:      $output[3]="inf-variance=0";
  618:      $output[4]="inf-variance=0";
  619:      return @output;
  620:   }
  621:   $output[3]=$skew/($sdev**3*$N);
  622:   $output[4]=$kurt/($sdev**4*$N)-3;
  623:   return @output;
  624: }
  625: 
  626: sub choose {
  627:   my $num = $_[0];
  628:   return $_[$num];
  629: }
  630: 
  631: 

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