Using variables from a .mat data file in a user-defined function

I'm writing a function that will read data from a .mat data file and interpret a message using ASCII binary. The input data has a series of frequencies, the target frequencies being from 400-750 Hz by increments of 50. If there is a peak at one of the frequencies it is interpreted as a 1 and stored in a string, otherwise it is interpreted as a zero. The error I am running into is the function is not recognizing the variables that are defined within the .mat file that I load into in my main script. The script and the function are shown below. Any help is appreciated I'm still fairly new to MATLAB.

load('message_1.mat'); %load in data signal

window_size = 50e-3; %set the window size to 50 ms
samples_per_window = window_size*fs; %calcalute number of samples in each 
                                     %window
total_windows = length(tone)/samples_per_window; %total number of sample
                                                 %windows
Message = [];
for i = 1:total_windows %repeats loop for total number of sample windows
    window = tone((i-1)*samples_per_window+1:i*samples_per_window); %define 
                        %the window within the tone data                   
    [X,f] = myFFT(window, fs); %perform the fourier transform
    Message = decipher(window, fs);
    

it should be noted I am using another user-defined function here myFFT

and then the user-defined function, decipher

    function [Message] = decipher(window,fs)

    binarystring = [];
    for n = 1:8 
        if abs(X(abs(f-(350+50*n)) < .01)) > 0.015
            binarystring=[binarystring '1'];
        else
            binarystring=[binarystring '0'];
        end
    end
    hold = char(bin2dec(binarystring)); % ASSIGN TO TEMP VAR
    Message = [Message hold]; % PUT VAR IN STRING TO DISPLAY LATER
    disp(Message)
    end

[Stephen23]

If you want to learn how to write robust MATLAB code and avoid these kind of errors, then LOAD into an output variable (which is a scalar structure) and access its fields:

S = load('message_1.mat'); %load in data signal

Your current approach (spamming unknown variables straight into the workspace) is always liable to these kind of bugs.

Answer 1

[Sulaymon Eshkabilov]

Note that the variable names stored and loaded from your *.mat file have to be consistent with the variable names called in your main m-file or to be renamed respectively so that your main m-file recalls the loaded variables correctly.

Answer 2

[Walter Roberson]

    function [Message] = decipher(window,fs)

            if abs(X(abs(f-(350+50*n)) < .01)) > 0.015

How is the code to know where to look for X? How is it to know where to look for f?

See http://www.mathworks.com/help/matlab/math/parameterizing-functions.html