Vector Length Error when Calling Function

function data = sandwichSummary(filename)
data = readcell(filename)
data(1,end+1) = {'PPI'}
length = data(2:end,2)
length = cell2mat(length)
price = data(2:end,3)
price = cell2mat(price)
PPI = round(price./length,2)
data(2:end,4) = num2cell(PPI)
avg_PPI = round(mean(PPI),2)
x_values1 = 1:length(PPI)% <- line that errors !!!! 
plot(x_values1,PPI,'gd')
hold on
[max1, location1] = max(PPI)
plot(location1,max1,'rd')
[min1,location2] = min(PPI)
plot(location2,min1,'cd')
x_values2 = 1:length(PPI)
y_values(1:length(PPI)) = avg_PPI
plot(x_values2,y_values,'m-')
title('Sandwich Summary')
xlabel('Menu Item')
ylabel('Prices')
end

When I try to call this function, it errors on the line that I noted above. The error message says, "Array indices must be positive integers or logical values". I am thoroughly confused on what that means because I have never had this problem before, and I use the "length" function quite frequently. Just for reference, I have included a screenshot of what is stored in the PPI variable. It is of type double.

Answer 1

[Voss]

You have a variable called "length":

length = data(2:end,2)

Later, on this line:

x_values1 = 1:length(PPI)

the existence of the variable "length" prevents the built-in function length from being called. Instead, MATLAB tries to index the variable "length" with index PPI, which produces the error.

The solution is to call your variable "length" something else.

Answer 2

[Torsten]

You overwrite MATLAB's intrinsic "length" in the lines

length = data(2:end,2)
length = cell2mat(length)