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In this video, we discuss the difference between the max and pmax functions in R. Pmax stands for parallel maximum.
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Welcome to the Data Hall YouTube channel
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In this video we are going to talk about what is the difference between the max and the
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p max which stands for parallel max functions. So what is the difference between these two functions
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For that let's have two vectors we have this v1 and v2 that contain these two vectors that
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contain certain numbers. Now if we do max v1 what it would do is it would take this vector and get the maximum
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value from it which should be 12. So let me execute this and we see that we get 12 over here
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If I do that for vector 2 we should get 10 because that is the maximum number in this
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v2 vector. Similarly we can have minimum values from both these vectors and both these vectors
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have the minimum value as 1. But what would p max do is instead of getting the maximum value from this vector or from
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this vector or if I were to give them say both these vectors within this this max function
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if we give that both these vectors within this max function what it would do is it would
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get me the maximum number from both of these vectors. But what if I wanted to have a parallel max that means I want to compare this value with
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the first value of the v1 with the first value of the v2 and then I want to get the maximum
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number then I want to do that process similarly for the second value and the third value and
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so forth. So once one way of doing this is to loop through each of these values and loop are an inefficient
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way of performing this. The more efficient way of doing is using the p max
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So what we do is within p max we give both these vectors and it would return the vector
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of the same length so it would compare one the first value of the v1 vector with the
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first value of the v2 vector and it returns us the value 2 then it would do that for the
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second value the third value and so on and so forth. If we just give them a single vector then it would return that specific vector because
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that is the maximum value. We can similarly do minimum p minimum and that will return the minimum value between
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these two vectors. Now what if we have a vector of different length and what if we have some missing values
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within these vectors. So this is a vector of the same vector as we had over here but we have shortened the
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length of v2 and we have also included in Na missing value within this v2
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So let me redefine v1 and v2 and now if we do p max firstly it would give us a warning
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that we that the second the smaller vector had been recycled that is the that is the
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by default system of R that it recycles the smaller vector and at the same time it would
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give us the Na value within because it when it compares the Na with some other digit it
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would return us the Na value. So what if first of all I wanted to remove the Na values so what I do is I use the Na
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dot rm equal to true argument and that would remove the Na values right and it would not
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take into consideration the Na values. So I hope that was useful
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