# Solved: remove nan

Sure, I will start with the problem of removing NaN values in MATLAB, which is a common issue programmers face when working.

NaN (Not a Number) is a value that is undefined or unrepresentable, often occurring when a mathematical operation fails to produce a specific numeric value. In MATLAB, missing or undefined data is represented with the term ‘NaN’. While this can be helpful, there are several situations where NaN values are troublesome and need to be eliminated.

## Addressing the NaN Issue in MATLAB

Handling and removing NaN values in a MATLAB vector or matrix is a common routine process in data analysis. Often, the NaN values are inconsequential to the rest of the data and can be removed without affecting the integrity of the research or analysis. Here are some methods you can use to remove NaN elements from an array.

The function ‘isnan’ in MATLAB returns a logical array that identifies NaN elements in the original array. ‘isnan’ stands for ‘is not a number’, and the function will return 1 (true) for each NaN element in the original array and 0 (false) for any other element.

```A = [1 2 NaN; NaN 5 6; 7 8 NaN];
TF = isnan(A);
```

## Step-by-Step Explanation of the code

In the first line, we have defined a 3×3 array ‘A’ containing NaN values. In the next line, we use the isnan function to identify the NaN values in ‘A’. The isnan function peruses through ‘A’ and returns a corresponding value (1 or 0) for NaN (1) and for NOT NaN (0). The output ‘TF’ will be a 3×3 array showing the position of NaN values as ‘True’ in ‘A’.

```TF =
0     0     1
1     0     0
0     0     1
```

Replacing or Removing NaN values

To remove NaN values from the array, one of the commonly used functions is ‘find’. The find function finds the indices of array elements that meet a certain condition, and in this case, we’re looking for ‘not a number’ elements. Then, it removes these indices from the array, effectively removing the NaN values.

```[i, j] = find(isnan(A));
A(i,j) = [];
```

## Solutions with Specific MATLAB Libraries or Functions

Another way is to use the built-in functions. One of these is ‘rmmissing’, which was introduced in MATLAB R2017b. With ‘rmmissing’, you can remove any row or column with a missing value (NaN) in a matrix or table.

```A = rmmissing(A);
```

This function scans the array or table ‘A’, eliminates all rows containing NaN values, and reassigns the cleaned data back to ‘A’.

MATLAB provides convenience and an array of built-in functions to handle NaN issues meticulously. It’s best to familiarize yourself with these libraries to smoothly handle such issues in data analysis.

Note: Always be cautious when removing NaN or missing values, as sometimes these values are there for a reason and simply removing them could skew your data or results. Always thoroughly understand your data and the context before proceeding to remove or replace NaN values.

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