cat ${nwo_file} \
    | gawk \
        -v dir="${dir}" \
        -i ./error_funcs.gawk \
        ' BEGIN { 
            inf = "+inf" + 0; dir += 0;
            vstep = -1; nh = 0; ndat=0;
            pwd = 0.15; eps = 0.005; 
            printf "dir = %d\n", dir > "/dev/stderr";
          }
          /^ *[-+0-9.]/ { 
            if (NF != 4) { data_error("bad NF") }
            ndat++;
            plo = $1 + dir*eps; vmd = $2 + dir*eps; phi = $3 + dir*eps; ct = $4 + dir*eps;
            pmd = vmd + dir*(eps + pwd/2); plo = pmd - pwd/2; phi = pmd + pwd/2;
            if (ct > 0) {
              print "";
              print plo, 0; print plo, ct;
              print phi, ct; print phi, 0;
              nh++;
            }
            next;
          }
          // { data_error("bad format"); }
          END { 
            printf "%5d histogram entries\n", ndat > "/dev/stderr";
            printf "%5d non-zero histogram bars\n", nh > "/dev/stderr";
            if (nh == 0) { bug("no bins"); }
            print "";
          }
        ' \
    > ${dat_file}