diff --git a/Graphs/gGraphView.cpp b/Graphs/gGraphView.cpp
index 94d3f84b..31a31003 100644
--- a/Graphs/gGraphView.cpp
+++ b/Graphs/gGraphView.cpp
@@ -1370,36 +1370,25 @@ void gGraph::resize(int width, int height)
 
 qint64 gGraph::MinX()
 {
-    bool first=true;
     qint64 val=0,tmp;
     for (QVector<Layer *>::iterator l=m_layers.begin();l!=m_layers.end();l++) {
         if ((*l)->isEmpty()) continue;
         tmp=(*l)->Minx();
-        if (!tmp) continue;
-        if (first) {
-            val=tmp;
-            first=false;
-        } else {
-            if (tmp < val) val = tmp;
-        }
+        //if (!tmp) continue;
+        if (!val || tmp < val) val = tmp;
     }
     if (val) rmin_x=val;
     return val;
 }
 qint64 gGraph::MaxX()
 {
-    bool first=true;
+    //bool first=true;
     qint64 val=0,tmp;
     for (QVector<Layer *>::iterator l=m_layers.begin();l!=m_layers.end();l++) {
         if ((*l)->isEmpty()) continue;
         tmp=(*l)->Maxx();
-        if (!tmp) continue;
-        if (first) {
-            val=tmp;
-            first=false;
-        } else {
-            if (tmp > val) val = tmp;
-        }
+        //if (!tmp) continue;
+        if (!val || tmp > val) val = tmp;
     }
     if (val) rmax_x=val;
     return val;
@@ -1412,7 +1401,8 @@ EventDataType gGraph::MinY()
     for (QVector<Layer *>::iterator l=m_layers.begin();l!=m_layers.end();l++) {
         if ((*l)->isEmpty()) continue;
         tmp=(*l)->Miny();
-        if (tmp==0 && tmp==(*l)->Maxy()) continue;
+        if (tmp==0 && tmp==(*l)->Maxy())
+            continue;
         if (first) {
             val=tmp;
             first=false;
@@ -1443,11 +1433,11 @@ EventDataType gGraph::MaxY()
 
 void gGraph::SetMinX(qint64 v)
 {
-    rmax_x=min_x=v;
+    rmin_x=min_x=v;
 }
 void gGraph::SetMaxX(qint64 v)
 {
-    rmin_x=max_x=v;
+    rmax_x=max_x=v;
 }
 void gGraph::SetMinY(EventDataType v)
 {
@@ -1721,8 +1711,19 @@ void gGraphView::scrollbarValueChanged(int val)
 void gGraphView::ResetBounds(bool refresh) //short group)
 {
     for (int i=0;i<m_graphs.size();i++) {
-        //if (m_graphs[i]->group()==group)
-            m_graphs[i]->ResetBounds();
+        m_graphs[i]->ResetBounds();
+    }
+
+    if (PROFILE["LinkGroups"].toBool()) {
+        qint64 m1=0,m2=0;
+        for (int i=0;i<m_graphs.size();i++) {
+            if (!m1 || m_graphs[i]->min_x<m1) m1=m_graphs[i]->min_x;
+            if (!m2 || m_graphs[i]->max_x>m2) m2=m_graphs[i]->max_x;
+        }
+        for (int i=0;i<m_graphs.size();i++) {
+            m_graphs[i]->SetMinX(m1);
+            m_graphs[i]->SetMaxX(m2);
+        }
     }
     qint64 xx=m_graphs[0]->max_x-m_graphs[0]->min_x;
     double d=xx/86400000L;
@@ -1731,7 +1732,6 @@ void gGraphView::ResetBounds(bool refresh) //short group)
     int s=(xx/1000) % 60;
     int ms(xx % 1000);
     QString str;
-
     if (d>1) {
         str.sprintf("%1.0f days",ceil(double(xx)/86400000.0));
     } else {
@@ -1746,8 +1746,9 @@ void gGraphView::ResetBounds(bool refresh) //short group)
 void gGraphView::SetXBounds(qint64 minx, qint64 maxx,short group,bool refresh)
 {
     for (int i=0;i<m_graphs.size();i++) {
-        if (m_graphs[i]->group()==group)
+        if (PROFILE["LinkGroups"].toBool()|| (m_graphs[i]->group()==group)) {
             m_graphs[i]->SetXBounds(minx,maxx);
+        }
     }
     qint64 xx=maxx-minx;
     double d=xx/86400000L;
diff --git a/Graphs/gSummaryChart.cpp b/Graphs/gSummaryChart.cpp
index 72d8e039..b75932c5 100644
--- a/Graphs/gSummaryChart.cpp
+++ b/Graphs/gSummaryChart.cpp
@@ -105,12 +105,13 @@ void SummaryChart::SetDay(Day * nullday)
         if (fnd) {
             if (!m_fday) m_fday=dn;
             m_values[dn][0]=total;
+            m_hours[dn]=day->hours();
             if (m_graphtype==GT_BAR) {
                 if (total<m_miny) m_miny=total;
                 if (total>m_maxy) m_maxy=total;
             }
             m_empty=false;
-       }
+       } else m_hours[dn]=0;
     }
     if (m_graphtype==GT_BAR) {
         m_miny=0;
@@ -202,8 +203,8 @@ void SummaryChart::paint(gGraph & w,int left, int top, int width, int height)
     double total_val=0;
     qint64 lastQ=0;
     bool lastdaygood=false;
-    QVector<int> totalcounts;
-    QVector<EventDataType> totalvalues;
+    QVector<double> totalcounts;
+    QVector<double> totalvalues;
     //QVector<EventDataType> lastvalues;
     QVector<float> lastX;
     QVector<short> lastY;
@@ -242,6 +243,7 @@ void SummaryChart::paint(gGraph & w,int left, int top, int width, int height)
     }
 
     Day * day;
+    EventDataType hours;
     for (qint64 Q=minx;Q<=maxx+86400000L;Q+=86400000L) {
         zd=Q/86400000L;
         d=m_values.find(zd);
@@ -250,6 +252,7 @@ void SummaryChart::paint(gGraph & w,int left, int top, int width, int height)
         if (Q<minx) continue;
         if (d!=m_values.end()) {
             day=m_days[zd];
+            hours=m_hours[zd];
 
             int x1=px;
             //x1-=(barw/2.0);
@@ -284,10 +287,11 @@ void SummaryChart::paint(gGraph & w,int left, int top, int width, int height)
                 } else if (m_type[j]==ST_MIN) {
                     if (tmp<totalvalues[j]) totalvalues[j]=tmp;
                 } else {
-                    totalvalues[j]+=tmp;
+                    totalvalues[j]+=tmp*hours;
                 }
-                if (tmp)
-                    totalcounts[j]++;
+                //if (tmp) {
+                    totalcounts[j]+=hours;
+                //}
                 tmp-=miny;
                 h=tmp*ymult; // height in pixels
 
@@ -357,7 +361,7 @@ void SummaryChart::paint(gGraph & w,int left, int top, int width, int height)
         if ((m_type[j]==ST_MIN) || (m_type[j]==ST_MAX)) {
             f=totalvalues[j];
         } else {
-            f=totalvalues[j]/float(totalcounts[j]);
+            f=totalvalues[j]/totalcounts[j];
         }
         if (m_type[j]==ST_HOURS) {
             int h=f;
diff --git a/Graphs/gSummaryChart.h b/Graphs/gSummaryChart.h
index 7ead41ac..7457b1ed 100644
--- a/Graphs/gSummaryChart.h
+++ b/Graphs/gSummaryChart.h
@@ -33,6 +33,7 @@ class SummaryChart:public Layer
         QVector<ChannelID> m_codes;
         QVector<SummaryType> m_type;
         QHash<int,QHash<short,EventDataType> > m_values;
+        QHash<int,EventDataType> m_hours;
         QHash<int,Day *> m_days;
 
         GLShortBuffer *quads,*lines;
diff --git a/daily.cpp b/daily.cpp
index fbfde781..ac1833fb 100644
--- a/daily.cpp
+++ b/daily.cpp
@@ -191,6 +191,8 @@ Daily::Daily(QWidget *parent,gGraphView * shared, MainWindow *mw)
     SPO2->AddLayer(AddOXI(new gLineChart(OXI_SPO2,Qt::blue,true)));
     PLETHY->AddLayer(AddOXI(new gLineChart(OXI_Plethy,Qt::darkBlue,false)));
 
+    SPO2->forceMinY(60);
+    PULSE->forceMinY(40);
     for (int i=0;i<ng;i++){
         graphs[i]->AddLayer(new gYAxis(),LayerLeft,gYAxis::Margin);
         graphs[i]->AddLayer(new gXAxis(),LayerBottom,0,20);
@@ -614,6 +616,14 @@ void Daily::Load(QDate date)
             tmp.sprintf(("<tr><td align=center>%08i</td><td align=center>"+fd.date().toString(Qt::SystemLocaleShortDate)+"</td><td align=center>"+fd.toString("HH:mm ")+"</td><td align=center>"+ld.toString("HH:mm")+"</td></tr>").toLatin1(),(*s)->session());
             html+=tmp;
         }
+        for (QVector<Session *>::iterator s=oxi->begin();s!=oxi->end();s++) {
+            fd=QDateTime::fromTime_t((*s)->first()/1000L);
+            ld=QDateTime::fromTime_t((*s)->last()/1000L);
+            QHash<ChannelID,QVariant>::iterator i=(*s)->settings.find("BrokenWaveform");
+            if ((i!=(*s)->settings.end()) && i.value().toBool()) corrupted_waveform=true;
+            tmp.sprintf(("<tr><td align=center>%08i</td><td align=center>"+fd.date().toString(Qt::SystemLocaleShortDate)+"</td><td align=center>"+fd.toString("HH:mm ")+"</td><td align=center>"+ld.toString("HH:mm")+"</td></tr>").toLatin1(),(*s)->session());
+            html+=tmp;
+        }
         html+="</table>";
         if (corrupted_waveform) {
             html+="<hr><div align=center><i>One or more waveform record for this session had faulty source data. Some waveform overlay points may not match up correctly.</i></div>";
diff --git a/docs/channels.xml b/docs/channels.xml
index 83dc0b10..4622f7b3 100644
--- a/docs/channels.xml
+++ b/docs/channels.xml
@@ -10,9 +10,9 @@ One id code per item
   <!-- Channel List -->
   <channel id="0x1000" class="data" name="CSR" details="Cheyne Stokes Respiration" label="CSR" color="light green"/>
   <channel id="0x1001" class="data" name="ClearAirway" details="Clear Airway Apnea" label="CA" color="purple"/>
-  <channel id="0x1002" class="data" name="Obstructive" details="Obstructive Apnea" label="O" color="#40c0ff"/>
+  <channel id="0x1002" class="data" name="Obstructive" details="Obstructive Apnea" label="OA" color="#40c0ff"/>
   <channel id="0x1003" class="data" name="Hypopnea" details="Hypopnea" label="H" color="blue"/>
-  <channel id="0x1004" class="data" name="Apnea" details="Unspecified Apnea" label="A" color="dark green"/>
+  <channel id="0x1004" class="data" name="Apnea" details="Unspecified Apnea" label="UA" color="dark green"/>
   <channel id="0x1005" class="data" name="FlowLimit" details="Flow Limitation" label="FL" color="dark grey"/>
   <channel id="0x1006" class="data" name="RERA" details="Respiratory Effort Related Arousal" label="RERA" color="gold"/>
   <channel id="0x1007" class="data" name="VSnore" details="Vibratory Snore" label="VS" unit="" color="red"/>
diff --git a/mainwindow.cpp b/mainwindow.cpp
index 7750263c..7821f494 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -110,6 +110,7 @@ MainWindow::MainWindow(QWidget *parent) :
     if (!PROFILE.Exists("EnableMultithreading")) PROFILE["EnableMultithreading"]=QThread::idealThreadCount()>1;
     if (!PROFILE.Exists("MemoryHog")) PROFILE["MemoryHog"]=false;
     if (!PROFILE.Exists("EnableGraphSnapshots")) PROFILE["EnableGraphSnapshots"]=false;
+    if (!PROFILE.Exists("LinkGroups")) PROFILE["LinkGroups"]=true;
     if (!PROFILE.Exists("AlwaysShowOverlayBars")) PROFILE["AlwaysShowOverlayBars"]=0;
     if (!PROFILE.Exists("UseAntiAliasing")) PROFILE["UseAntiAliasing"]=false;
     if (!PROFILE.Exists("IntentionalLeak")) PROFILE["IntentionalLeak"]=(double)0.0;
@@ -120,7 +121,7 @@ MainWindow::MainWindow(QWidget *parent) :
 
 
     //ui->actionUse_AntiAliasing->setChecked(PROFILE["UseAntiAliasing"].toBool());
-
+    ui->action_Link_Graph_Groups->setChecked(PROFILE["LinkGroups"].toBool());
 
     first_load=true;
 
@@ -464,3 +465,9 @@ void MainWindow::on_action_Edit_Profile_triggered()
     newprof.exec();
 
 }
+
+void MainWindow::on_action_Link_Graph_Groups_toggled(bool arg1)
+{
+    PROFILE["LinkGroups"]=arg1;
+    if (daily) daily->ReloadGraphs();
+}
diff --git a/mainwindow.h b/mainwindow.h
index d8044fb8..1a08e96b 100644
--- a/mainwindow.h
+++ b/mainwindow.h
@@ -92,6 +92,8 @@ private slots:
 
     void on_action_Edit_Profile_triggered();
 
+    void on_action_Link_Graph_Groups_toggled(bool arg1);
+
 private:
     Ui::MainWindow *ui;
     Daily * daily;
diff --git a/mainwindow.ui b/mainwindow.ui
index 163ef4c9..1089620d 100644
--- a/mainwindow.ui
+++ b/mainwindow.ui
@@ -593,6 +593,7 @@
     <addaction name="action_Fullscreen"/>
     <addaction name="action_Screenshot"/>
     <addaction name="separator"/>
+    <addaction name="action_Link_Graph_Groups"/>
     <addaction name="action_Reset_Graph_Layout"/>
    </widget>
    <widget class="QMenu" name="menu_Help">
@@ -674,14 +675,6 @@
     <string>&amp;About SleepyHead</string>
    </property>
   </action>
-  <action name="action_Link_Graphs">
-   <property name="checkable">
-    <bool>true</bool>
-   </property>
-   <property name="text">
-    <string>&amp;Link Graphs</string>
-   </property>
-  </action>
   <action name="action_Fullscreen">
    <property name="checkable">
     <bool>true</bool>
@@ -693,14 +686,6 @@
     <string>F11</string>
    </property>
   </action>
-  <action name="action_Noon_Date_Split">
-   <property name="checkable">
-    <bool>true</bool>
-   </property>
-   <property name="text">
-    <string>&amp;Noon Date Split</string>
-   </property>
-  </action>
   <action name="actionDebug">
    <property name="checkable">
     <bool>true</bool>
@@ -709,39 +694,11 @@
     <string>Debug</string>
    </property>
   </action>
-  <action name="actionOverlay_Bars">
-   <property name="checkable">
-    <bool>true</bool>
-   </property>
-   <property name="text">
-    <string>&amp;Overlay Bars</string>
-   </property>
-  </action>
-  <action name="action_Memory_Hog">
-   <property name="checkable">
-    <bool>true</bool>
-   </property>
-   <property name="text">
-    <string>&amp;Memory Hog</string>
-   </property>
-  </action>
   <action name="action_Reset_Graph_Layout">
    <property name="text">
     <string>&amp;Reset Graph Layout</string>
    </property>
   </action>
-  <action name="actionEnable_Multithreading">
-   <property name="checkable">
-    <bool>true</bool>
-   </property>
-   <property name="text">
-    <string>Enable Multithreading</string>
-   </property>
-   <property name="toolTip">
-    <string>Warning: Enabling this feature may require you to either hand edit the Preferences.xml or delete SleepyHeads data folder.
-</string>
-   </property>
-  </action>
   <action name="actionCheck_for_Updates">
    <property name="text">
     <string>Check for &amp;Updates</string>
@@ -773,6 +730,14 @@
     <string>&amp;Edit Profile</string>
    </property>
   </action>
+  <action name="action_Link_Graph_Groups">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="text">
+    <string>&amp;Link Graph Groups</string>
+   </property>
+  </action>
  </widget>
  <customwidgets>
   <customwidget>
diff --git a/overview.cpp b/overview.cpp
index a834a677..57d10434 100644
--- a/overview.cpp
+++ b/overview.cpp
@@ -79,8 +79,8 @@ Overview::Overview(QWidget *parent,gGraphView * shared) :
 
     set=new SummaryChart("",GT_LINE);
     //set->addSlice("SysOneResistSet",QColor("grey"),ST_SETAVG);
-    set->addSlice("HumidSet",QColor("blue"),ST_SETAVG);
-    set->addSlice("FlexSet",QColor("red"),ST_SETAVG);
+    set->addSlice("HumidSet",QColor("blue"),ST_SETWAVG);
+    set->addSlice("FlexSet",QColor("red"),ST_SETWAVG);
     //set->addSlice("PAPMode",QColor("red"),ST_SETAVG);
     SET->forceMinY(0);
     SET->forceMaxY(5);