First Semester in Numerical Analysis with Julia, 2020a

CHAPTER 5. APPROXIMATION THEORY 192
19.8
19.1
27.1
31.0
27.0
22.7
The next step is to store the part of the data we need as an array. The function
select takes two arguments: the name of the table, and the column heading the contents
of which will be stored as an array. In our table there is only one column named Temp.
In [4]: temp=select(data, :Temp);
Let’s check the type of temp, its first entry, and its length:
In [5]: typeof(temp)
Out[5]: Array{Float64,1}
In [6]: temp[1]
Out[6]: 28.7
In [7]: length(temp)
Out[7]: 1056
There are 1,056 temperature values. The x-coordinates are the days, numbered
t =1, 2, ..., 1056. Here is the array that stores these time values:
In [8]: time=[i for i=1:1056];
Next we define the matrix A, taking advantage of the fact the matrix is symmetric.
The function sum(x) adds the entries of the array x.
In [9]: A=zeros(4,4);
A[1,1]=1056
A[1,2]=sum(time)
A[1,3]=sum(t->sin(2*pi*t/365),time)