## WeBWorK Problems

### horizontal line prevents PDF output

by Hedley Pinsent -
Number of replies: 4

FYI

The file works fine on the screen but PDF output is prevented.

## DESCRIPTION

#
# First comes some stuff that appears at the beginning of every problem
#

DOCUMENT();        # This should be the first executable line in the problem.

"PGbasicmacros.pl",

);

TEXT($BEGIN_ONE_COLUMN,beginproblem()) ; BEGIN_TEXT The horizonntal line as a seperator prevents PDF output$PAR

_________________________________________________
$PAR The end END_TEXT TEXT($END_ONE_COLUMN);

ENDDOCUMENT();        # This should be the last executable line in the problem.

### Re: horizontal line prevents PDF output

by D. Brian Walton -
PDF output puts your displayed problem through a LaTeX engine for interpretation. The error arises because you created your horizontal line using an underscore "_". In LaTeX this symbol is reserved for subscripts and must be in math-mode. This is the source for the error. You would not see the error if you used hyphens "-", although the display would not be as nice.

I'm not yet sure how to get customize display between on-screen and hard-copy. If I see how to do that, I'll repost later.

D. Brian Walton
In reply to D. Brian Walton

### Re: horizontal line prevents PDF output

by Arnold Pizer -
Hi,

As Dick points out, many simple things (such as a horizontal rule) have already been defined so that you can get the correct output in hardcopy output (pdf using LaTeX) and in html output on the screen.

The answer to Brian's question as how to "get customize display between on-screen and hard-copy" is to use the MODES command.  I'm not sure where or if this is documented on the wiki, but you can see an example of its use in the file ASimpleCombinedHeaderFile.pg which you will find in the templates directory of every course if you have a relatively recent installation of WeBWorK. If you have an older installation and do not have that file, you can see it online: http://webwork.maa.org/viewvc/system/trunk/webwork2/courses.dist/modelCourse/templates/ASimpleCombinedHeaderFile.pg?revision=6856&view=markup

If you have access to the WeBWorK code, you can see how the horizontal rule and other similar things are defined in the file  /opt/webwork/pg/macros/PGbasicmacros.pl
If you don't have direct access to the code, you can view the file online at http://webwork.maa.org/viewvc/system/trunk/pg/macros/PGbasicmacros.pl?revision=6929&view=markup

Arnie

by Dick Lane -
Would  $HR (described at http://webwork.maa.org/wiki/Display_Macros) serve your purpose? In reply to Dick Lane ### Re: horizontal line prevents PDF output by Hedley Pinsent - Yes$HR . . . and I did see this before??
Can't wait until somebody writes a book.

Anyway I also wanted a real backslash \ but used a dash instead.
It was to identify the headings and columns of a table.

Actually it all has to do with a chi-squared test of a contingency table (statistics)
Here is the example if anybody is interested.

## DESCRIPTION
## Statistics
## ENDDESCRIPTION

## KEYWORDS('Statistics','Distribution')
## Tagged by

## DBsubject('Statistics')
## DBchapter('Chi-squared')
## DBsection('Contingency Table')
## Date('April 2012')
## Author('Hedley Pinsent')
## Institution('CNA')
## TitleText1('')
## EditionText1('')
## AuthorText1('')
## Section1('')
## Problem1('')

#
# First comes some stuff that appears at the beginning of every problem
#

DOCUMENT(); # This should be the first executable line in the problem.

"PGbasicmacros.pl",
"PGchoicemacros.pl",

"unionMacros.pl",
"unionTables.pl",

"PGstatisticsmacros.pl",

);

TEXT($BEGIN_ONE_COLUMN,beginproblem()) ; # vvvvvvvvvvvvvvvvv Defining Categories while ($nRows + $nColumns < 5){$nRows = list_random(2,3,4);
$nColumns = list_random(2,3,4)} @colourList = ("Red","Green","Yellow","Blue","Orange", "Purple"); @colaList = ("Inca","Pepsi","Coca-Cola","Mountain Dew","Lime","Frosty"); @colaList = @colaList[NchooseK(6,$nRows)];
@colourList = @colourList[NchooseK(6,$nColumns)]; # ^^^^^^^^^^^^^^^^^ Defining Categories ## Constructing Differences vvvvvvvvvvvvvvvvvvvvvv foreach$irow (0..$nRows -1){ foreach$icol (0..$nColumns -1){$D[$irow*$nColumns + $icol] = 0;# Differences = zeros } } #adjust below to get balance between reject and do not reject$tries = random(1,5,1);

foreach $i (0..$tries){
$diff = list_random(1,2,3,4,5, -5,-4,-3,-2,-1); @colPair = NchooseK($nColumns, 2);
@rowPair = NchooseK($nRows, 2);$D[$rowPair[0]*$nColumns + $colPair[0]] +=$diff;
$D[$rowPair[0]*$nColumns +$colPair[1]] -= $diff;$D[$rowPair[1]*$nColumns + $colPair[1]] +=$diff;
$D[$rowPair[1]*$nColumns +$colPair[0]] -= $diff; } ## Constructing Differences ^^^^^^^^^^^^^^^^^^^^^^ # Assigning Values (Expected/Observed) vvvvvvvvvvvvvvvvvvvvvvv$base = random (1,3,1);
foreach $irow (0..$nRows -1){$rowFact[$irow]= list_random(4,5,6,7,8,9)}
foreach $icol (0..$nColumns -1){$colFact[$icol]= list_random(4,5,6,7,8,9)}

foreach $irow (0..$nRows -1){
foreach $icol (0..$nColumns -1){

$E[$irow*$nColumns +$icol] = $base*$rowFact[$irow]*$colFact[$icol];# Expected$O[$irow*$nColumns + $icol] =$E[$irow*$nColumns + $icol]+$D[$irow*$nColumns + $icol];# Observed } } # Assigning Values (Expected/Observed)^^^^^^^^^^^^^^^^^^^^^^ ##Calculating chi-squared vvvvvvvvvvvvvvvvvvvvvvvvv$CALC = 0;
foreach $k (0..$nRows * $nColumns -1){$CALC =$CALC + ($D[$k]**2) /$E[$k]} ##Calculating chi-squared ^^^^^^^^^^^^^^^^^^^^^^^^ ##Constructing the data table vvvvvvvvvvvvvvvvvvvvvvvvvvvvv$datatable = BeginTable(spacing => 3);
$datatable .= AlignedRow(["Cola-Colour",@colourList]); foreach$i (0..$nRows-1) { foreach$j (0.. $nColumns -1) { @row [$j] = $O[$i *$nColumns +$j];
}

$datatable .= AlignedRow([$colaList[$i],@row]) }$datatable .= EndTable();

##Constructing the data table ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

BEGIN_TEXT

Follows is a contingency table for colour preference and cola preference. $BR For example$O[0 *$nColumns + 0] people in the survey preferred the colour$colourList[0] and their favourite beverage was $colaList[0]$PAR
$datatable END_TEXT ##Constructing the answer table vvvvvvvvvvvvvvvvvvvvvvvvvvvvv$answertable = BeginTable(spacing => 3);
$answertable .= AlignedRow(["Cola-Colour",@colourList, "Totals"]); foreach$i (0..$nRows-1) {$rowTotal = 0;
foreach $j (0..$nColumns -1) {

$name =$i . "and". $j; @answerRule[$j] = NAMED_ANS_RULE($name,6); push @namedCmp ,$name=>num_cmp( $E[$i *$nColumns +$j] ) ;
$rowTotal =$rowTotal + $E[$i *$nColumns +$j] ;
$colTotal[$j] = $colTotal[$j]+ $E[$i *$nColumns +$j];
}
$name = "rowTotal".$i;

@answerRule[$nColumns] = NAMED_ANS_RULE($name,6);
push @namedCmp , $name=>num_cmp($rowTotal ) ;
$answertable .= AlignedRow([$colaList[$i],@answerRule]); } # Last row foreach$k (0..$nColumns-1 ){$name = "colTotal".$k; @answerRule[$k] = NAMED_ANS_RULE($name,6); push @namedCmp ,$name=>num_cmp( $colTotal[$k] ) ;
}
$grandTotal = 0; foreach$k (0..$nColumns - 1){$grandTotal += $colTotal[$k]}
$name = "grand";$answerRule[$nColumns] = NAMED_ANS_RULE($name,6);
push @namedCmp , $name=>num_cmp($grandTotal ) ;
$answertable .= AlignedRow(["Totals",@answerRule]);$answertable .= EndTable();

BEGIN_TEXT

For the above table calculate the row totals, column totals grand total, and the expected values. $BR Enter these values in the appropriate spaces below.$PAR

$answertable END_TEXT ## Setting up significance test vvvvvvvvvvvvvvvvvvvvvvvvvvv$alpha = list_random(0.01,0.05);
$df = ($nColumns -1)*($nRows - 1);$CRIT = chisqrdistr ($df,$alpha);

##Setting up significance test ^^^^^^^^^^^^^^^^^^^^^^^^^^^

$mcnull = new_multiple_choice();$mcnull->qa(
"",
"There is no relationship"
);
$mcnull->extra( "There is a relationship" );$mcalt = new_multiple_choice();
$mcalt->qa( "", "There is a relationship" );$mcalt->extra(
"There is no relationship"
);

##SETTING UP THE TABLE

@r1 = ("$$H_0$$", $mcnull->print_a()) ; @r2 = ("$$H_1$$",$mcalt->print_a());

$mcTestStatistic = new_multiple_choice();$mcTestStatistic->qa(
"The test statistic is",
"$$\chi^2$$"
);
$mcTestStatistic->extra( "$$z$$", "$$t$$","$$F$$", ); # Test Statistics choices$mctestEQ = new_multiple_choice();
$mctestEQ->qa( "", "$$\gt$$" );$mctestEQ->extra("$$\lt or \gt$$". " -/+",

"$$\lt$$"
);

@r3 = ("We reject if: ", $mcTestStatistic->print_a() ,$mctestEQ->print_a(),NAMED_ANS_RULE("CRIT",6));

$mcAR = new_multiple_choice(); ## this is a two-tailed test if( abs($CALC) >$CRIT ){$mcAR->qa(
"We",
"reject"
);
$mcAR->extra( "do not reject" );} else{$mcAR->qa(
"We",
"do not reject"
);
$mcAR->extra( "reject" );} BEGIN_TEXT$HR

At a $alpha significance level test whether there is a relationship between favourite colour and farourite cola.$PAR

$PAR \{begintable(4)\} \{row( @r1)\} \{row( @r2)\} \{endtable()\}$PAR

$PAR $$\alpha$$ = \{NAMED_ANS_RULE("alpha",6)\}$PERCENT $BR$BR

\{begintable(4)\}
\{row( @r3)\}
\{endtable()\}
$PAR The value of the test statistic is \{NAMED_ANS_RULE("Ftest",6)\}$PAR

\{$mcAR->print_q()\} \{$mcAR->print_a()\}

END_TEXT

##contingency table check vvvvvvvvvvvvvvvvvv

NAMED_ANS(@namedCmp);

##contingency table check ^^^^^^^^^^^^^^^^^^

#CHECKING FIRST ROW H0
ANS( radio_cmp( $mcnull->correct_ans() ) ); #CHECKING SECOND ROW H1 ANS( radio_cmp($mcalt->correct_ans() ) );

#checking alpha in percent
NAMED_ANS(alpha=>num_cmp( 100 * $alpha, mode=>"arith", reltol=>.01)); #CHECKING THIRD ROW ANS( radio_cmp($mcTestStatistic->correct_ans() ) );
ANS( radio_cmp( $mctestEQ->correct_ans() ) ); NAMED_ANS(CRIT=>num_cmp($CRIT, mode=>"arith", reltol=>2));
#CHECKING FORTH ROW

NAMED_ANS(Ftest=>num_cmp( $CALC, mode=>"arith", reltol=>2)); ANS( radio_cmp($mcAR->correct_ans() ) );

TEXT(\$END_ONE_COLUMN);

ENDDOCUMENT(); # This should be the last executable line in the problem.