Código PHP:
$vars_actitud = $db->select_one("SELECT variables FROM factores WHERE titulo = 'Actitud'");
$array_vars_actitud = explode(",",$vars_actitud);
$cant_vars_array_actitud = count($array_vars_actitud);
$letras = array('1' => 'A',
'2' => 'B',
'3' => 'C',
'4' => 'D',
'5' => 'E',
'6' => 'F',
'7' => 'G',
'8' => 'H',
'9' => 'I',
'10' => 'J',
'11' => 'K',
'12' => 'L',
'13' => 'M',
'14' => 'O',
'15' => 'P',
'16' => 'Q',
'17' => 'R',
'18' => 'S',
'19' => 'T',
'20' => 'U');
for($i=0; $i<=($cant_vars_array_actitud - 1); $i++):
$sql = "SELECT COUNT(*) FROM la_tabla WHERE ";
$sql .= $array_vars_actitud[$i];
$sql .= " = 1 AND MONTH(fecha) = ";
$sql .= $fecha_form;
$vars = $db->select_one($sql);
$DataSet->AddPoint($vars, "Serie1");
$DataSet->AddPoint($umbral_actitud, "Serie2");
$DataSet->AddPoint(array($letras[$i]), "Serie4");
endfor;
gracias.