Getting a series trend line equation to a shape text box - vba

Question

I'm attempting to get the trend line equation from the first series in my chart to a shape text box placed elsewhere on the worksheet - however, I can only get the textbox to populate correctly when I'm stepping through the code line by line - during run-time it has no effect:
For Each chtObj In ActiveSheet.ChartObjects
Set cht = chtObj.Chart
For Each srs In chtObj.Chart.SeriesCollection
srs.Trendlines(1).DisplayEquation = True 'Display the labels to get the value
ThisWorkbook.Worksheets("MyDataSheet").Shapes(slopetextboxes(k)).TextFrame.Characters.Text = srs.Trendlines(1).DataLabel.Text
srs.Trendlines(1).DisplayEquation = False 'Turn it back off
Exit For
Next srs
k = k + 1 ' for the slope textboxes
Next chtObj
Note that slopetextboxes is an array containing the names of ~6 shape text boxes.
As far as I know there's no way to get the trend line data label without stopping to display it. I've tried storing it in a string first, DoEvents, and turning Application.ScreenUpdating back on, all to no avail. I'm stumped here.
EDIT: It appears that by placing DoEvents after .DisplayEquation = True I'm able to have some of my shapes populate correctly, but not all. Still appears to be some kind of run-time issue.
BOUNTY EDIT: I've moved ahead to grab the slopes with a formula ran into the data itself, but I still don't understand why I can't grab the chart's .DataLabel.Text during run-time. I can grab it when stepping through, not during run-time. It appears to just take the PREVIOUS series slope and place it in the shape (or a cell, it doesn't even matter where the destination is). DoEvents placed in different spots yields different outcomes, so something must be going on.

Answer 1

Updated with better understanding of the bug. This works for me in excel 2016 with multiple changes to the source data (and therefore the slope)
I tried myChart.refresh - didnt work. I tried deleting and then re-adding the entire trendline, also didnt work.
This works for everything but the first case. First case needs to be hit twice. Same as for .select
If you try and delete trendline even after assigning its text to textbox, this wont work
Option Explicit
Sub main()
Dim ws As Worksheet
Dim txtbox As OLEObject
Dim chartObject As chartObject
Dim myChart As chart
Dim myChartSeriesCol As SeriesCollection
Dim myChartSeries As Series
Dim myChartTrendLines As Trendlines
Dim myTrendLine As Trendline
Set ws = Sheets("MyDataSheet")
Set txtbox = ws.OLEObjects("TextBox1")
For Each chartObject In ws.ChartObjects
Set myChart = chartObject.chart
Set myChartSeriesCol = myChart.SeriesCollection
Set myChartSeries = myChartSeriesCol(1)
Set myChartTrendLines = myChartSeries.Trendlines
With myChartTrendLines
If .Count = 0 Then
.Add
End If
End With
Set myTrendLine = myChartTrendLines.Item(1)
With myTrendLine
.DisplayEquation = True
txtbox.Object.Text = .DataLabel.Text
End With
Next chartObject
End Sub

Answer 2

Here's my code that seems to definitely work when just pressing F5:
Basically, I store the text in a collection, then iterate through all of the textboxes to add the text to the textboxes. If this wasn't precisely what you were asking for, then I hope this helps in any way.
Sub getEqus()
Dim ws As Worksheet
Dim cht As Chart
Dim srs As Variant
Dim k As Long
Dim i As Long
Dim equs As New Collection
Dim shp As Shape
Dim slopetextboxes As New Collection
Set ws = Excel.Application.ThisWorkbook.Worksheets(1)
'part of the problem seemed to be how you were defining your shape objects
slopetextboxes.Add ws.Shapes.Range("TextBox 4")
slopetextboxes.Add ws.Shapes.Range("TextBox 5")
For Each chtObj In ActiveSheet.ChartObjects
Set cht = chtObj.Chart
For Each srs In chtObj.Chart.SeriesCollection
srs.Trendlines(1).DisplayEquation = True 'Display the labels to get the value
equs.Add srs.Trendlines(1).DataLabel.Text
srs.Trendlines(1).DisplayEquation = False 'Turn it back off
Next srs
Next chtObj
For i = 1 To slopetextboxes.Count
'test output i was trying
ws.Cells(i + 1, 7).Value = equs(i)
slopetextboxes(i).TextFrame.Characters.Text = equs(i)
Next
End Sub
Pictures of what the output looks like when i just press the button
Good luck!

Answer 3

This worked for me - I loop through multiple charts on Sheet1, toggling DisplayEquation and then writing the equation to a textbox/shape on the different worksheet. I used TextFrame2.TextRange but TextFrame worked as well, if you prefer that. I wrote to both a regular text box, as well as a shape, which was probably overkill as the syntax is the same for both.
This gets the trendline equation from the first Series - it sounded like you didn't want to loop through all the Series in the SeriesCollection.
Sub ExtractEquations()
Dim chtObj As ChartObject
Dim slopeTextBoxes() As Variant
Dim slopeShapes() As Variant
Dim i As Integer
slopeTextBoxes = Array("TextBox 1", "TextBox 2", "TextBox 3")
slopeShapes = Array("Rectangle 6", "Rectangle 7", "Rectangle 8")
For Each chtObj In ThisWorkbook.Sheets("Sheet1").ChartObjects
With chtObj.Chart.SeriesCollection(1).Trendlines(1)
.DisplayEquation = True
ThisWorkbook.Sheets("MyDataSheet").Shapes(slopeTextBoxes(i)).TextFrame2.TextRange.Characters.Text = .DataLabel.Text
ThisWorkbook.Sheets("MyDataSheet").Shapes(slopeShapes(i)).TextFrame2.TextRange.Characters.Text = .DataLabel.Text
.DisplayEquation = False
i = i + 1
End With
Next chtObj
End Sub

Answer 4

I've written this off as a bug - The only workaround was discovered by BrakNicku which is to Select the DataLabel before reading its Text property:
srs.Trendlines(1).DataLabel.Select
Not a sufficient solution (since this can cause some issues during run-time), but the only thing that works.

Answer 5

I had a similar issue running the code below and my solution was to run Application.ScreenUpdating = True between setting the trendline and querying the DataLabel. Note that screen updating was already enabled.
'Set trendline to the formal y = Ae^Bx
NewTrendline.Type = xlExponential
'Display the equation on the chart
NewTrendline.DisplayEquation = True
'Add the R^2 value to the chart
NewTrendline.DisplayRSquared = True
'Increse number of decimal places
NewTrendline.DataLabel.NumberFormat = "#,##0.000000000000000"
'Enable screen updating for the change in format to take effect otherwise FittedEquation = ""
Application.ScreenUpdating = True
'Get the text of the displated equation
FittedEquation = NewTrendline.DataLabel.Text

Answer 6

If it works when you step through, but not when it runs then it's an issue with timing and what Excel is doing in between steps. When you step through, it has time to figure things out and update the screen.
FYI, Application.Screenupdating = False doesn't work when stepping
through code. It gets set back to True wherever the code pauses.
When did you give it a chance to actually do the math and calculate the equation? The answer is that, you didn't; hence why you get the previous formula.
If you add a simple Application.Calculate (in the right spot) I think you'll find that it works just fine.
In addition, why should Excel waste time and update text to an object that isn't visible? The answer is, it shouldn't, and doesn't.
In the interest of minimizing the amount of times you want Excel to calculate, I'd suggest creating two loops.
The first one, to go through each chart and display the equations
Then force Excel to calculate the values
Followed by another loop to get the values and hide the equations again.
' Display the labels on all the Charts
For Each chtObj In ActiveSheet.ChartObjects
Set cht = chtObj.Chart
For Each srs In chtObj.Chart.SeriesCollection
srs.Trendlines(1).DisplayEquation = True 'Display the labels to get the value
' I take issue with the next line
' Why are you creating a loop, just for the first series?
' I hope this is just left over from a real If condition that wan't included for simplicity
Exit For
Next srs
Next chtObj
Application.ScreenUpdating = True
Application.Calculate
Application.ScreenUpdating = False
' Get the Equation and hide the equations on the chart
For Each chtObj In ActiveSheet.ChartObjects
Set cht = chtObj.Chart
For Each srs In chtObj.Chart.SeriesCollection
ThisWorkbook.Worksheets("MyDataSheet").Shapes(slopetextboxes(k)).TextFrame.Characters.Text = srs.Trendlines(1).DataLabel.Text
srs.Trendlines(1).DisplayEquation = False 'Turn it back off
Exit For
Next srs
k = k + 1 ' for the slope textboxes
Next chtObj
Application.ScreenUpdating = True
Update:
I added a sample file based on your description of the issue. You can select 4 different options in an ActiveX ComboBox which copies values to the Y-Values of a chart. It shows the trend-line equation below, based on the formula & through copying the value from the chart into a Textbox shape.
Maybe 2016 is different, but it works perfectly in 2013. Try it out...
Shape Text Box Example.xlsm