You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: visualizeBoundary.m
    path of file: ./repos/machine-learning-coursera-1/Week 7 Assignments/Support Vector Machines/mlclass-ex6
    
    the code of the file until where you have to start completion: function visualizeBoundary(X, y, model, varargin)
%VISUALIZEBOUNDARY plots a non-linear decision boundary learned by the SVM
%   VISUALIZEBOUNDARYLINEAR(X, y, model) plots a non-linear decision 
%   boundary learned by the SVM and overlays the data on it


    
function visualizeBoundary(X, y, model, varargin)
%VISUALIZEBOUNDARY plots a non-linear decision boundary learned by the SVM
%   VISUALIZEBOUNDARYLINEAR(X, y, model) plots a non-linear decision 
%   boundary learned by the SVM and overlays the data on it

% Plot the training data on top of the boundary
plotData(X, y)

% Make classification predictions over a grid of values
x1plot = linspace(min(X(:,1)), max(X(:,1)), 100)';
x2plot = linspace(min(X(:,2)), max(X(:,2)), 100)';
[X1, X2] = meshgrid(x1plot, x2plot);
vals = zeros(size(X1));
for i = 1:size(X1, 2)
   this_X = [X1(:, i), X2(:, i)];
   vals(:, i) = svmPredict(model, this_X);
end