Accessing value of a variable inside a function
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I have a variable, " c " defined outside a function as shown (just an example):
c=5;
function sum = add(a, b)
sum = a+b+c
end
Calling the add function by giving inputs for a, b Matlab throws an error saying : Local function name must be different from the script name. I want the value of the variable "c" to be accessed within the function so that if I give input of (2,3) for (a,b) I should be getting an output of sum = 10. Everything works fine if the variable " c " is inside the function but doesnt work when its outside the function. I tried to globally define the variable "c" like:
global c
c=5;
function sum = add(a, b)
global c
sum = a+b+c
end
But still Mathlab throws an error. Can anybody help me with this?
1 个评论
Stephen23
2020-12-30
I suspect that you should be parameterizing the function:
Avoid global variables, they cause more problems than they solve.
采纳的回答
Image Analyst
2020-12-30
The global case should not throw an error. However you should not use sum or add as the name of your variables since they're already built-in functions. Is the function in the same m-file as the script? When I do this, all in the same m-file, it works fine:
global c
c=5;
s = myAddition(10, 20)
function theSum = myAddition(a, b)
global c
theSum = a+b+c
end
So, does that work for you? If not, what did you do differently?
2 个评论
Mahith Madhana Kumar
2020-12-30
Image Analyst
2020-12-30
Do not call it add.m. That could cause a problem with the other built-in add functions. So rename it and upload/attach it here. If it's essentially the same as mine, it should run fine.
更多回答（1 个）
Walter Roberson
2020-12-30
编辑：Walter Roberson
2020-12-30
0 个投票
When you define a script, and you define a function inside the script, then the name of the function cannot be the same as the name of the script.
Also, when you define a variable in a script, functions defined in the script do not have access to the variable. Shared variables are possible only with nested functions.
I suggest that you read
9 个评论
Mahith Madhana Kumar
2020-12-30
编辑：Mahith Madhana Kumar
2020-12-30
Image Analyst
2020-12-30
Upload add.m, time.m, and frequency.m.
Mahith Madhana Kumar
2020-12-30
编辑：Mahith Madhana Kumar
2020-12-30
Please find attached time.m and frequency.m files. You might also need the other attached files alongside to run without error.
frequency.m is the file which you should be running to see the output (others contain functions that aid the smooth running of frequency.m file)
Also below is the screenshots from the code where you could find the variables ff and freq ( NOTE: ff is defined inside frequency.m file and freq is defined inside the function of time.m file)
There are a couple of things more to avoid errors before running frequency.m file:
1) You might have to change the path in readGPS_using_fresnel_frequency.m file (line 9) since it contains mine at the moment.
2) You also might need to download BSFK function and install it from: https://www.mathworks.com/matlabcentral/fileexchange/25872-free-knot-spline-approximation
My problem is this:
When I run frequency.m with ff (=pp.breaks(2)) as defined in frequency.m and with freq=ff as in time.m I ge the below error saying : " unrecognized function or variable ' ff '.
However, if I explicitly type in the value of ff found after running frequency.m (one of the outputs seen in the command window is ff) and equate it to freq in time.m then I am not getting any errors and I am getting the results correctly.
For instance, suppose I got a value of ff = 0.8880 (in the command window) after running frequency.m. I now manually equate this value of 0.8880 with the variable freq in time.m (instead of freq = ff) as shown below:
This gives me the correct output (the one of interest to me is shown below):
Now when I change it back to freq=ff in time.m and run frequency.m I still get the same output as above (this time without any error). It seems that somehow the variable freq remembers the previous value and outputs result based on that. However, when I delete the folder in my path and run frequency.m again with freq=ff in time.m I am getting back the error ( However, I dont get any error even after I delete the folder in my path and run frequency.m again but with freq=0.888 ).
I am not sure what is happening. I have like thousands of ff values and manually equating every ff values to freq and then deleting the folder in the path everytime seems not practical.
Is there any way to automatically equate the ff values from frequency.m to freq=ff in time.m so that for every different ff value, I get the corresponding outputs (without the need to delete the folder in the path and without the need to manually enter the ff value).
Thanks.
Walter Roberson
2020-12-30
You cannot normally access a variable defined inside another function, but see
Mahith Madhana Kumar
2020-12-30
Image Analyst
2020-12-30
Did you put
global ff;
inside BOTH frequency.m AND time.m?
Mahith Madhana Kumar
2020-12-30
Yes I did that as shown:
This is in frequency.m file
and this is in time.m file
Mahith Madhana Kumar
2020-12-31
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