diff --git a/even_stream_arrow.m b/even_stream_arrow.m
index a8584ae..66f910e 100755
--- a/even_stream_arrow.m
+++ b/even_stream_arrow.m
@@ -18,7 +18,7 @@
 %   'ArrowLength': arrow head length in pixels, default = 20
 %   'ArrowTipAngle': arrow head tip angle in degrees, default = 20
 %   'ArrowBaseAngle': arrow head base angle in degrees, default = 10
-%   'ArrowSpace': arrow head spacing along line in coordinate unite, 
+%   'ArrowSpace': arrow head spacing along line in data coordinate units, 
 %       default = 5% of minimum coordinate axis range
 %   
 % Returns:
diff --git a/even_stream_demo.m b/even_stream_demo.m
index 49299f7..bcf4bea 100755
--- a/even_stream_demo.m
+++ b/even_stream_demo.m
@@ -99,15 +99,14 @@
 
 % compute
 tic
-% xy = even_stream_data(xx, yy, dzdx, dzdy, 0.003, 0.0015);
-xy = even_stream_data(xx, yy, dzdx, dzdy, 0.05, 0.025);
+xy = even_stream_data(xx, yy, dzdx, dzdy, 0.003, 0.0015);
 fprintf('even_stream_data: %.3f s elapsed\n', toc);
 
 % plot
 tic
 hf = figure;
 hf.Name = sprintf('%s: even stream texture', mfilename);
-even_stream_texture(xy, 'LineWidth', 1, 'Period', 20);
+even_stream_texture(xy, 'LineWidth', 1, 'Period', 0.020*range(vv));
 title('even\_stream\_texture');
 ax = gca;
 ax.XTick = [];
diff --git a/even_stream_texture.m b/even_stream_texture.m
index e3e329b..f3bb8f5 100755
--- a/even_stream_texture.m
+++ b/even_stream_texture.m
@@ -12,7 +12,8 @@
 %
 % Optional Parameters (Name, Value):
 %   'LineWidth': line width, as in the plot(), default = 0.5
-%   'Period': length of periodic pattern in # points, default = 20;
+%   'Period': length of periodic pattern in data coordinate spacing, 
+%       default = 20% of minimum coordinate axis range
 %   
 % Returns:
 %   hh = Vector of graphics objects for streamlines
@@ -32,15 +33,19 @@
 parser.KeepUnmatched = false;
 
 parser.addParameter('LineWidth', 0.5);
-parser.addParameter('Period', 20);
+parser.addParameter('Period', 0.20*min(range(xy)));
 
 parser.parse(varargin{:});
 line_width = parser.Results.LineWidth;
 period = parser.Results.Period;
 
-validateattributes(period, {'numeric'}, {'scalar', 'positive', 'integer'}, ...
+validateattributes(period, {'numeric'}, {'scalar', 'positive'}, ...
     mfilename, 'period');
 
+% convert period to approximate number of points
+mean_segment_length = nanmean(sqrt(sum(diff(xy).^2, 2)));
+period = round(period/mean_segment_length);
+
 % reformat streamlines as segments 
 num_segments = size(xy, 1)-2*sum(isnan(xy(:,1)))-1;
 x_segment = nan(num_segments, 2);