Documentation of map_contour_pn

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Function Synopsis

[c, h] = map_contour(data, cint, usezero);

Help text

  [c, h] = map_contour(data, cint, usezero);

  data = map data
  cint:     if scalar, then it's the contour interval
            if vector, then it's a vector of contours levels
  usezero:  'zeroline', 'z', 'yes', 'y', or 1 will produce a zero line
            'nozeroline', 'n', or 0 will produce no zero line
            Default is 'nozeroline'

  This function uses the mapping toolbox to contour the
  input 'data' matrix.  It assumes that the x and y axes
  are defined in the global variables XAX and YAX, 
  respectively.

Cross-Reference Information

Listing of function map_contour_pn

function [c, h] = map_contour(data, cint, usezero);

%  Dan Vimont, 2 September, 1999

if nargin < 3; usezero = 0; end;
if isstr(usezero);
  if strcmp(lower(usezero(1)), 'z'); usezero = 1;
  elseif strcmp(lower(usezero(1)), 'y'); usezero = 1;
  elseif strcmp(lower(usezero(1)), 'n'); usezero = 0;
  else
    error('usezero must be either ''zeroline'', or ''nozeroline'' ');
  end
else
  if ~ismember([0 1], usezero);
    error('zeroline must be 0 (nozeroline) or 1 (zeroline)')
  end
end

data = squeeze(data);

%  First, determine if hold is 'on', or 'off'.

next_ax = lower(get(gca, 'NextPlot'));
if strcmp(next_ax, 'replace');  cla;  end;

%  Get the global varaibles XAX YAX and FRAME

global XAX YAX FRAME
if (size(XAX, 1) == 1); XAX = XAX'; end;
if (size(YAX, 1) == 1); YAX = YAX'; end;

[m, n] = size(data);
if or((m~=length(YAX)), (n~=length(XAX)));
  error('[length(YAX) length(XAX)] must equal size(data)');
end

%  Set defaults

if nargin < 2; cint = (max(max(data))-min(min(data)))/10; end;
lab = 0;
line_style = 'k';

%  Redefine XAX, YAX and data for global contouring -- allowing 
%  for wrapping around the globe.

[xk, yk] = keep_var(FRAME, XAX, YAX);
if (FRAME(2) - FRAME(1) == 360);
  data2 = [data(yk,:) data(yk,1)];
  XAX2 = [XAX; XAX(1)+360];
else
  data2 = data(yk,xk);
  XAX2 = XAX(xk);
end;
YAX2 = YAX(yk);

%  Define contour interval;

if isscalar(cint);
  clev = sort([-cint:-cint:min(min(data2)) ...
                cint:cint:max(max(data2))]);
else
  clev = cint;
end

if usezero; clev = sort([clev 0]); end

%  Repeat the first and last elements of clev, so if there's only
%  one positive or negative contour, it still works in pncontm.
%  Otherwise, it interprets it as the number of contour intervals
%  you want to use (see contourm).

clev = [clev(1) clev clev(end)];

%  Plot the data

[c, h] = pncontm(XAX2, YAX2, data2, clev, lab, line_style);

set(gca, 'NextPlot', next_ax);