diff --git a/doc/xschem_man/graphs.html b/doc/xschem_man/graphs.html
index fdbce825..050c5898 100644
--- a/doc/xschem_man/graphs.html
+++ b/doc/xschem_man/graphs.html
@@ -188,12 +188,22 @@ p{padding: 15px  30px 10px;}
   <li><kbd>sin()</kbd> Trig. sin function</li>
   <li><kbd>cos()</kbd> Trig. cos function</li>
   <li><kbd>tan()</kbd> Trig. tan function</li>
+  <li><kbd>sinh()</kbd> Hyp. sin function</li>
+  <li><kbd>cosh()</kbd> Hyp. cos function</li>
+  <li><kbd>tanh()</kbd> Hyp. tan function</li>
+  <li><kbd>asinh()</kbd> Inv hyp. sin function</li>
+  <li><kbd>acosh()</kbd> Inv hyp. cos function</li>
+  <li><kbd>atanh()</kbd> Inv hyp. tan function</li>
+  <li><kbd>asin()</kbd> Inverse trig. sin function</li>
+  <li><kbd>acos()</kbd> Inverse trig. cos function</li>
+  <li><kbd>atan()</kbd> Inverse trig. tan function</li>
   <li><kbd>sqrt()</kbd> Square root</li>
   <li><kbd>sgn()</kbd> Sign</li>
   <li><kbd>abs()</kbd> Absolute value</li>
   <li><kbd>exp()</kbd> Base-e Exponentiation</li>
   <li><kbd>ln()</kbd> Base-e logarithm</li>
   <li><kbd>log10()</kbd> Base 10 logarithm</li>
+  <li><kbd>idx()</kbd> point number (0, 1, 2, ...) in vector</li>
   <li><kbd>db20()</kbd> Value in deciBel (20 * log10(n))</li>
   <li><kbd>avg()</kbd> Average</li>
   <li><kbd>prev()</kbd> Delay waveform by one point (at any x-axis position take the previous value)</li>
diff --git a/src/save.c b/src/save.c
index c1571b43..b7cc5714 100644
--- a/src/save.c
+++ b/src/save.c
@@ -1459,6 +1459,7 @@ static double ravg_store(int what , int i, int p, int last, double value)
 #define ATANH 35
 #define ACOSH 36
 #define ASINH 37
+#define IDX 38 /* index of point in raw file (0, 1, 2, ...) */
 
 
 #define ORDER_DERIV 1 /* 1 or 2: 1st order or 2nd order differentiation. 1st order is faster */
@@ -1525,6 +1526,7 @@ int plot_raw_custom_data(int sweep_idx, int first, int last, const char *expr, c
     else if(!strcmp(n, "asinh()")) stack1[stackptr1++].i = ASINH;
     else if(!strcmp(n, "exp()")) stack1[stackptr1++].i = EXP;
     else if(!strcmp(n, "ln()")) stack1[stackptr1++].i = LN;
+    else if(!strcmp(n, "idx()")) stack1[stackptr1++].i = IDX;
     else if(!strcmp(n, "log10()")) stack1[stackptr1++].i = LOG10;
     else if(!strcmp(n, "integ()")) {
       if(first > 0) first--;
@@ -1589,7 +1591,6 @@ int plot_raw_custom_data(int sweep_idx, int first, int last, const char *expr, c
       else if(stack1[i].i == SPICE_NODE && stack1[i].idx < xctx->raw->nvars) { /* spice node */
         stack2[stackptr2++] =  xctx->raw->values[stack1[i].idx][p];
       }
-
       if(stackptr2 > 1) { /* 2 argument operators */
         switch(stack1[i].i) {
           case PLUS:
@@ -1681,7 +1682,7 @@ int plot_raw_custom_data(int sweep_idx, int first, int last, const char *expr, c
             break;
         } /* switch(...) */
       } /* if(stackptr2 > 1) */
-      if(stackptr2 > 0) { /* 1 argument operators */
+      else if(stackptr2 > 0) { /* 1 argument operators */
         switch(stack1[i].i) {
           case AVG:
             if( p == first ) {
@@ -1880,6 +1881,9 @@ int plot_raw_custom_data(int sweep_idx, int first, int last, const char *expr, c
           case LOG10:
             stack2[stackptr2 - 1] =  mylog10(stack2[stackptr2 - 1]);
             break;
+          case IDX:
+            stack2[stackptr2 - 1] = (double)p;
+            break;
           case DB20:
             stack2[stackptr2 - 1] =  20 * mylog10(stack2[stackptr2 - 1]);
             break;
@@ -1889,6 +1893,11 @@ int plot_raw_custom_data(int sweep_idx, int first, int last, const char *expr, c
             break;
         } /* switch(...) */
       } /* if(stackptr2 > 0) */
+      else if(stackptr2 == 0) {
+        if(stack1[i].i == IDX) {
+          stack2[stackptr2] = (double)p;
+        }
+      }
     } /* for(i = 0; i < stackptr1; ++i) */
     y[p] = (SPICE_DATA)stack2[0];
   } /* for(p = first ...) */