Radiobuttons and plotting - GUI question? - Homework

I am trying to make a GUI where it plots the cosine function from 1 to 100. There is a button group to allow the user to change the curve color. At beginning the cosine curve should be plotted in green color (not sure how to do this part) and the user can change it to red and blue. I am not sure what I am doing wrong but I don't get a curve. Here is my script below and attached.

function varargout = cosrgb(varargin)
% COSRGB MATLAB code for cosrgb.fig
%      COSRGB, by itself, creates a new COSRGB or raises the existing
%      singleton*.
%
%      H = COSRGB returns the handle to a new COSRGB or the handle to
%      the existing singleton*.
%
%      COSRGB('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in COSRGB.M with the given input arguments.
%
%      COSRGB('Property','Value',...) creates a new COSRGB or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before cosrgb_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to cosrgb_OpeningFcn via varargin.
%
%      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
%      instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES

% Edit the above text to modify the response to help cosrgb

% Last Modified by GUIDE v2.5 29-Nov-2013 23:48:57

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @cosrgb_OpeningFcn, ...
                   'gui_OutputFcn',  @cosrgb_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end

if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT

% --- Executes just before cosrgb is made visible.
function cosrgb_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to cosrgb (see VARARGIN)

% Choose default command line output for cosrgb
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

% UIWAIT makes cosrgb wait for user response (see UIRESUME)
% uiwait(handles.figure1);

% --- Outputs from this function are returned to the command line.
function varargout = cosrgb_OutputFcn(hObject, eventdata, handles) 
% varargout  cell array for returning output args (see VARARGOUT);
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% Get default command line output from handles structure
varargout{1} = handles.output;

% --- Executes on button press in radiobutton1.
function radiobutton1_Callback(hObject, eventdata, handles)
% hObject    handle to radiobutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hint: get(hObject,'Value') returns toggle state of radiobutton1

fplot('cos', [0, 100],'r');
xlabel('x');
ylabel('cos(x)');

% --- Executes on button press in radiobutton2.
function radiobutton2_Callback(hObject, eventdata, handles)
% hObject    handle to radiobutton2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hint: get(hObject,'Value') returns toggle state of radiobutton2
fplot('cos', [0, 100], 'g');
xlabel('x');
ylabel('cos(x)');

% --- Executes on button press in radiobutton3.
function radiobutton3_Callback(hObject, eventdata, handles)
% hObject    handle to radiobutton3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hint: get(hObject,'Value') returns toggle state of radiobutton3

fplot('cos', [0, 100], 'b');
xlabel('x');
ylabel('cos(x)');

???