How can the IF ELSE loop be applied to a data frame. I want the loop to take the first 2 columns as conditions and give me an output in the final. For eg: if “col A” == 4 && “col B” == 2 print(“Yes”) else print(“no”)

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A column of a dataframe is just a vector, so for (a, b) in zip(df.A, df.B) (a==4) & (b==2) ? print("Yes") : print("No") end

Or using broadcasting: f(a,b) = (a==4) & (b==2) ? "Yes" : "No" res = f.(df.A, df.B) println(res)

[image] lungben: res = f.(df.A, df.B) How do you interpret the function broadcast?

df.A and df.B are Arrays with the same length. The function f is applied to each “row” of the dataframe separately and its output is written into the array res. Hope this answers your question!

Does (df.A, df.B) == zip(df.A, df.B)?

No. zip(df.A, df.B) gives an array of (2-element) tuples, whereas (df.A, df.B) is a tuple of arrays.

So f.(df.A, df.B) applies f to every pair of arguments that it extracts from each row of columns df.A and df.B and returns a vector of “yes” or “no” strings?

Correct Example: df = DataFrame(a=(1:10).+2, b=1:10) f(a,b) = (a==4) & (b==2) ? "Yes" : "No" res = f.(df.a, df.b)

A few more details: the . after a function is syntactic sugar. All dotted functions on a line are fused into a single function and applied element-wise to their arguments using the higher-level function broadcast. So sin.(cos.(xs) .+ 1) == broadcast(x -> sin(cos(x) + 1), xs) The function broadcast …

If-else applied to a DataFrame

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xiaodai August 20, 2020, 4:31am 2

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If-else applied to a DataFrame

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