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# dtrend_leftdim

Estimates and removes the least squares linear trend of the leftmost dimension from all grid points and retains metadata.

## Prototype

```load "\$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"  ; This library is automatically loaded
; from NCL V6.2.0 onward.
; No need for user to explicitly load.

function dtrend_leftdim (
y               : numeric,
return_info  : logical
)

return_val [dimsizes(y)] :  numeric
```

## Arguments

y

An array with one or more dimensions, nominally, (time), (time,lat,lon), etc.

return_info

A logical scalar controlling whether attributes corresponding to the y-intercept and slope are attached to return_val. True = attributes returned. False = no attributes returned.

## Return value

An array of the same size as y. Double if y is double, float otherwise.

Two attributes (slope and y_intercept) may be attached to return_val if return_info = True. These attributes will be one-dimensional arrays if y is one-dimensional. If y is multi-dimensional, the attributes will be the same size as y . Double if return_val is double, float otherwise.

You access the attributes through the @ operator:

```print(return_val@slope)
print(return_val@y_intercept)
```

## Description

This is a utility function that behaves like dtrend/dtrend_n, except it retains metadata.

Before version 5.2.0, this function (a) reordered the input array, y; (b) used dtrend to detrend; and, (c) returned to the original dimension order. For version 5.2.0 and later, this function uses dtrend_n to avoid having to reorder the data.

```  yDtrend = dtrend_leftdim(y,False)