Add command 'linearnp np=1024 vec1 vec2'

linearises tran output on given number of time points.
If none is given, 2^n new points are chosen, next to
but smaller than original number of time points.

src/frontend/commands.c

@@ -642,6 +642,10 @@ struct comm spcp_coms[] = {
       { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 0, LOTS,
       NULL,
       " [ vec ... ] : Convert plot into one with linear scale." } ,
+    { "linearnp", com_linearnp, FALSE, FALSE,
+      { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 0, LOTS,
+      NULL,
+      " [ vec ... ] : Convert plot into one with linear scale, number of points given." },
     { "cutout", com_cutout, FALSE, FALSE,
       { 040000, 040000, 040000, 040000 }, E_DEFHMASK, 0, LOTS,
       NULL,

src/frontend/linear.c

@@ -130,6 +130,149 @@ com_linearize(wordlist *wl)
     }
 }
 
+/* Interpolate all the vectors in a plot to a linear time scale, which
+ * we determine by looking at the transient parameters in the CKT struct.
+ * If no circuit is loaded, e.g. because the 'load' command has been used
+ * to obtain data, try to get parameters from scale vector.
+ * Interpolation may be restricted to only a region of the input vector,
+ * thus creating a cutout of the original vector. The number of data points
+ * is given by parameter np=xx.
+ */
+void
+com_linearnp(wordlist* wl)
+{
+    double tstart, tstop, tstep, d;
+    struct plot* new, * old;
+    struct dvec* newtime, * v;
+    struct dvec* oldtime;
+    struct dvec* lin;
+    int expo, len, i;
+    wordlist* wlnew;
+
+    if (!plot_cur || !plot_cur->pl_typename || !ciprefix("tran", plot_cur->pl_typename)) {
+        fprintf(cp_err, "Error: plot must be a transient analysis\n");
+        return;
+    }
+    if (!plot_cur->pl_dvecs || !plot_cur->pl_scale) {
+        fprintf(cp_err, "Error: no vectors available\n");
+        return;
+    }
+    if (!isreal(plot_cur->pl_scale)) {
+        fprintf(cp_err, "Error: non-real time scale for %s\n",
+            plot_cur->pl_typename);
+        return;
+    }
+
+    /* check if circuit is loaded and TSTART, TSTOP, TSTEP are available
+       if no circuit is loaded, but vectors are available, obtain
+       start, stop, step data from scale vector */
+    if (!ft_curckt || !ft_curckt->ci_ckt ||
+        !if_tranparams(ft_curckt, &tstart, &tstop, &tstep)) {
+        fprintf(cp_err,
+            "Warning: Can't get transient parameters from circuit.\n"
+            "         Use transient analysis scale vector data instead.\n");
+        int length = plot_cur->pl_scale->v_length;
+        if (length < 1) {
+            fprintf(cp_err, "Error: no data in vector\n");
+            return;
+        }
+        tstart = plot_cur->pl_scale->v_realdata[0];
+        tstop = plot_cur->pl_scale->v_realdata[length - 1];
+        tstep = (tstop - tstart) / (double)length;
+    }
+
+    /* if this plot contains special vectors lin-tstart, lin-tstop or lin-tstep, use these instead */
+    lin = vec_fromplot("lin-tstart", plot_cur);
+    if (lin) {
+        fprintf(cp_out, "linearize tstart is set to: %8e\n", lin->v_realdata[0]);
+        tstart = lin->v_realdata[0];
+    }
+
+    lin = vec_fromplot("lin-tstop", plot_cur);
+    if (lin) {
+        fprintf(cp_out, "linearize tstop is set to: %8e\n", lin->v_realdata[0]);
+        tstop = lin->v_realdata[0];
+    }
+
+    lin = vec_fromplot("lin-tstep", plot_cur);
+    if (lin) {
+        fprintf(cp_out, "linearize tstep is set to: %8e\n", lin->v_realdata[0]);
+        tstep = lin->v_realdata[0];
+    }
+
+    /* finally check if tstart, tstop and tstep are reasonable */
+    if (((tstop - tstart) * tstep <= 0.0) || ((tstop - tstart) < tstep)) {
+        fprintf(cp_err,
+            "Error: bad parameters -- start = %G, stop = %G, step = %G\n",
+            tstart, tstop, tstep);
+        return;
+    }
+    old = plot_cur;
+    oldtime = old->pl_scale;
+    new = plot_alloc("transient");
+    new->pl_name = tprintf("%s (linearized)", old->pl_name);
+    new->pl_title = copy(old->pl_title);
+    new->pl_date = copy(old->pl_date);
+    new->pl_next = plot_list;
+    plot_new(new);
+    plot_setcur(new->pl_typename);
+    plot_list = new;
+
+    /* default number of points */
+    expo = (int)(log2((tstop - tstart) / tstep));
+    len = 1 << expo;
+
+    wlnew = wl;
+    /* get the new length from 'np=xx' */
+    while (wlnew) {
+        char* para = wlnew->wl_word;
+        if (ciprefix("np=", para)) {
+            para += 3;
+            len = atoi(para);
+            break;
+        }
+        wlnew = wlnew->wl_next;
+    }
+
+    tstep = (tstop - tstart) / (double)len;
+
+    newtime = dvec_alloc(copy(oldtime->v_name),
+        oldtime->v_type,
+        oldtime->v_flags | VF_PERMANENT,
+        len, NULL);
+
+    newtime->v_plot = new;
+    for (i = 0, d = tstart; i < len; i++, d += tstep)
+        newtime->v_realdata[i] = d;
+    new->pl_scale = new->pl_dvecs = newtime;
+
+    if (wl) {
+        while (wl) {
+            if (ciprefix("np=", wl->wl_word)) {
+                wl = wl->wl_next;
+                continue;
+            }
+            v = vec_fromplot(wl->wl_word, old);
+            if (!v) {
+                fprintf(cp_err, "Error: no such vector %s\n",
+                    wl->wl_word);
+                wl = wl->wl_next;
+                continue;
+            }
+            lincopy(v, newtime->v_realdata, len, oldtime);
+            wl = wl->wl_next;
+        }
+    }
+    else {
+        for (v = old->pl_dvecs; v; v = v->v_next) {
+            if (v == old->pl_scale)
+                continue;
+            lincopy(v, newtime->v_realdata, len, oldtime);
+        }
+    }
+}
+
+
 
 /* Cut out part of tran vectors from cut-tstart to cut-tstop and copy these
    into a new plot. A new scale vector 'time' will be there as well. Vectors

src/frontend/linear.h

@@ -7,6 +7,7 @@
 #define ngspice_LINEAR_H
 
 void com_linearize(wordlist *wl);
+void com_linearnp(wordlist *wl);
 void com_cutout(wordlist *wl);